js-apis-util.md

# util


> **NOTE**
>
> The initial APIs of this module are supported since API version 7. Newly added APIs will be marked with a superscript to indicate their earliest API version.


This module provides common utility functions, such as **TextEncoder** and **TextDecoder** for string encoding and decoding, **RationalNumber** for rational number operations, **LruBuffer** for buffer management, **Scope** for range determination, **Base64** for Base64 encoding and decoding, and **Types** for checks of built-in object types.


## Modules to Import

```
import util from '@ohos.util';
```

## util.printf

printf(format: string,  ...args: Object[]): string

Prints the input content in a formatted string.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| format | string | Yes| Format of the string to print.|
| ...args | Object[] | No| Data to format.|

**Return value**

| Type| Description|
| -------- | -------- |
| string | String in the specified format.|

**Example**
  ```js
  let res = util.printf("%s", "hello world!");
  console.log(res);
  ```


## util.getErrorString

getErrorString(errno: number): string

Obtains detailed information about a system error code.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| errno | number | Yes| Error code generated.|

**Return value**

| Type| Description|
| -------- | -------- |
| string | Detailed information about the error code.|

**Example**
  ```js
  let errnum = 10; // 10 is a system error code.
  let result = util.getErrorString(errnum);
  console.log("result = " + result);
  ```


## util.callbackWrapper

callbackWrapper(original: Function): (err: Object, value: Object )=>void

Calls back an asynchronous function. In the callback, the first parameter indicates the cause of the rejection (the value is **null** if the promise has been resolved), and the second parameter indicates the resolved value.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| original | Function | Yes| Asynchronous function.|

**Return value**

| Type| Description|
| -------- | -------- |
| Function | Callback, in which the first parameter indicates the cause of the rejection (the value is **null** if the promise has been resolved) and the second parameter indicates the resolved value.|

**Example**
  ```js
  async function promiseFn() {
      return Promise.reject('value');
  }
  let err = "type err";
  let cb = util.callbackWrapper(promiseFn);
  cb((err, ret) => {
      console.log(err);
      console.log(ret);
  }, err)
  ```


## util.promiseWrapper<sup>(deprecated)</sup>

promiseWrapper(original: (err: Object, value: Object) =&gt; void): Object

> **NOTE**
> This API is deprecated since API version 9. You are advised to use **[util.promisify9+](#utilpromisify9)** instead.

Processes an asynchronous function and returns a promise version.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| original | Function | Yes| Asynchronous function.|

**Return value**

| Type| Description|
| -------- | -------- |
| Function | Function in the error-first style (that is, **(err, value) =>...** is called as the last parameter) and the promise.|

## util.promisify<sup>9+</sup>

promisify(original: (err: Object, value: Object) =&gt; void): Function

Processes an asynchronous function and returns a promise.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| original | Function | Yes| Asynchronous function.|

**Return value**

| Type| Description|
| -------- | -------- |
| Function | Function in the error-first style (that is, **(err, value) =>...** is called as the last parameter) and the promise.|

**Example**
  ```js
  function aysnFun(str1, str2) {
    if (typeof str1 === 'object' && typeof str2 === 'object') {
      return str2
    } else {
      return str1
    }
  }
  let newPromiseObj = util.promisify(aysnFun);
  newPromiseObj({ err: "type error" }, {value:'HelloWorld'}).then(res => {
    console.log(res);
  })
  ```

## util.randomUUID<sup>9+</sup>

randomUUID(entropyCache?: boolean): string

Uses a secure random number generator to generate a random universally unique identifier (UUID) of RFC 4122 version 4.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| entropyCache | boolean | No| Whether a cached UUID can be used. The default value is **true**.|

**Return value**

| Type| Description|
| -------- | -------- |
| string | A string representing the UUID generated.|

**Example**
  ```js
  let uuid = util.randomUUID(true);
  console.log("RFC 4122 Version 4 UUID:" + uuid);
  // Output:
  // RFC 4122 Version 4 UUID:88368f2a-d5db-47d8-a05f-534fab0a0045
  ```

## util.randomBinaryUUID<sup>9+</sup>

randomBinaryUUID(entropyCache?: boolean): Uint8Array

Uses a secure random number generator to generate a random binary UUID of RFC 4122 version 4.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| entropyCache | boolean | No| Whether a cached UUID can be used. The default value is **true**.|

**Return value**

| Type| Description|
| -------- | -------- |
| Uint8Array | A Uint8Array value representing the UUID generated.|

**Example**
  ```js
  let uuid = util.randomBinaryUUID(true);
  console.log(JSON.stringify(uuid));
  // Output:
  // 138,188,43,243,62,254,70,119,130,20,235,222,199,164,140,150
  ```

## util.parseUUID<sup>9+</sup>

parseUUID(uuid: string): Uint8Array

Parses a UUID from a string, as described in RFC 4122 version 4.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| uuid | string | Yes| A string representing the UUID.|

**Return value**

| Type| Description|
| -------- | -------- |
| Uint8Array | A Uint8Array value representing the UUID parsed. If the parsing fails, **SyntaxError** is thrown.|

**Example**
  ```js
  let uuid = util.parseUUID("84bdf796-66cc-4655-9b89-d6218d100f9c");
  console.log(JSON.stringify(uuid));
  // Output:
  // 132,189,247,150,102,204,70,85,155,137,214,33,141,16,15,156
  ```

## TextDecoder

### Attributes

**System capability**: SystemCapability.Utils.Lang

| Name| Type| Readable| Writable| Description|
| -------- | -------- | -------- | -------- | -------- |
| encoding | string | Yes| No| Encoding format.<br>- Supported formats: utf-8, ibm866, iso-8859-2, iso-8859-3, iso-8859-4, iso-8859-5, iso-8859-6, iso-8859-7, iso-8859-8, iso-8859-8-i, iso-8859-10, iso-8859-13, iso-8859-14, iso-8859-15, koi8-r, koi8-u, macintosh, windows-874, windows-1250, windows-1251, windows-1252, windows-1253, windows-1254, windows-1255, windows-1256, windows-1257, windows-1258, x-mac-cyrilli, gbk, gb18030, big5, euc-jp, iso-2022-jp, shift_jis, euc-kr, utf-16be, utf-16le|
| fatal | boolean | Yes| No| Whether to display fatal errors.|
| ignoreBOM | boolean | Yes| No| Whether to ignore the byte order marker (BOM). The default value is **false**, which indicates that the result contains the BOM.|


### constructor

constructor(encoding?: string, options?: { fatal?: boolean; ignoreBOM?: boolean },)

A constructor used to create a **TextDecoder** object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| encoding | string | No| Encoding format.|
| options | Object | No| Encoding-related options, which include **fatal** and **ignoreBOM**.|

  **Table 1** options

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| fatal | boolean | No| Whether to display fatal errors.|
| ignoreBOM | boolean | No| Whether to ignore the BOM.|

**Example**
  ```js
  let textDecoder = new util.TextDecoder("utf-8",{ignoreBOM: true});
  ```


### decode

decode(input: Uint8Array, options?: { stream?: false }): string

Decodes the input content.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| input | Uint8Array | Yes| Uint8Array to decode.|
| options | Object | No| Options related to decoding.|

  **Table 2** options

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| stream | boolean | No| Whether to allow data blocks in subsequent **decode()**. If data is processed in blocks, set this parameter to **true**. If this is the last data block to process or data is not divided into blocks, set this parameter to **false**. The default value is **false**.|

**Return value**

| Type| Description|
| -------- | -------- |
| string | Data decoded.|

**Example**
  ```js
  let textDecoder = new util.TextDecoder("utf-8",{ignoreBOM: true});
  let result = new Uint8Array(6);
  result[0] = 0xEF;
  result[1] = 0xBB;
  result[2] = 0xBF;
  result[3] = 0x61;
  result[4] = 0x62;
  result[5] = 0x63;
  console.log("input num:");
  let retStr = textDecoder.decode( result , {stream: false});
  console.log("retStr = " + retStr);
  ```


### decodeWithStream<sup>9+</sup>

decodeWithStream(input: Uint8Array, options?: { stream?: boolean }): string

Decodes the input content.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| input | Uint8Array | Yes| Uint8Array to decode.|
| options | Object | No| Options related to decoding.|

  **Table 2** options

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| stream | boolean | No| Whether to allow data blocks in subsequent **decodeWithStream()**. If data is processed in blocks, set this parameter to **true**. If this is the last data block to process or data is not divided into blocks, set this parameter to **false**. The default value is **false**.|

**Return value**

| Type| Description|
| -------- | -------- |
| string | Data decoded.|

**Example**
  ```js
  let textDecoder = new util.TextDecoder("utf-8",{ignoreBOM: true});
  let result = new Uint8Array(6);
  result[0] = 0xEF;
  result[1] = 0xBB;
  result[2] = 0xBF;
  result[3] = 0x61;
  result[4] = 0x62;
  result[5] = 0x63;
  console.log("input num:");
  let retStr = textDecoder.decodeWithStream( result , {stream: false});
  console.log("retStr = " + retStr);
  ```


## TextEncoder

### Attributes

**System capability**: SystemCapability.Utils.Lang

| Name| Type| Readable| Writable| Description|
| -------- | -------- | -------- | -------- | -------- |
| encoding | string | Yes| No| Encoding format. The default format is **utf-8**.|


### constructor

constructor()

A constructor used to create a **TextEncoder** object.

**System capability**: SystemCapability.Utils.Lang

**Example**
  ```js
  let textEncoder = new util.TextEncoder();
  ```


### encode

encode(input?: string): Uint8Array

Encodes the input content.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| input | string | Yes| String to encode.|

**Return value**

| Type| Description|
| -------- | -------- |
| Uint8Array | Encoded text.|

**Example**
  ```js
  let textEncoder = new util.TextEncoder();
  let buffer = new ArrayBuffer(20);
  let result = new Uint8Array(buffer);
  result = textEncoder.encode("\uD800¥¥");
  ```


### encodeInto

encodeInto(input: string, dest: Uint8Array, ): { read: number; written: number }

Stores the UTF-8 encoded text.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| input | string | Yes| String to encode.|
| dest | Uint8Array | Yes| **Uint8Array** instance used to store the UTF-8 encoded text.|

**Return value**

| Type| Description|
| -------- | -------- |
| Uint8Array | Encoded text.|

**Example**
  ```js
  let that = new util.TextEncoder()
  let buffer = new ArrayBuffer(4)
  let dest = new Uint8Array(buffer)
  let result = new Object()
  result = that.encodeInto('abcd', dest)
  ```

## RationalNumber<sup>8+</sup>


### constructor<sup>8+</sup>

constructor(numerator: number,denominator: number)

A constructor used to create a **RationalNumber** object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| numerator | number | Yes| Numerator, which is an integer.|
| denominator | number | Yes| Denominator, which is an integer.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  ```


### createRationalFromString<sup>8+</sup>

static createRationalFromString​(rationalString: string): RationalNumber​

Creates a **RationalNumber** object based on the given string.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| rationalString | string | Yes| String used to create the **RationalNumber** object.|

**Return value**

| Type| Description|
| -------- | -------- |
| object | **RationalNumber** object created.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let rational = util.RationalNumber.createRationalFromString("3/4");
  ```


### compareTo<sup>8+</sup>

compareTo​(another: RationalNumber): number​

Compares this **RationalNumber** object with a given object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| another | RationalNumber | Yes| Object used to compare with this **RationalNumber** object.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Returns **0** if the two objects are equal; returns **1** if the given object is less than this object; return **-1** if the given object is greater than this object.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let rational = util.RationalNumber.createRationalFromString("3/4");
  let result = rationalNumber.compareTo(rational);
  ```


### valueOf<sup>8+</sup>

valueOf(): number

Obtains the value of this **RationalNumber** object as an integer or a floating-point number.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | An integer or a floating-point number.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let result = rationalNumber.valueOf();
  ```


### equals<sup>8+</sup>

equals​(obj: Object): boolean

Checks whether this **RationalNumber** object equals the given object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| object | Object | Yes| Object used to compare with this **RationalNumber** object.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the two objects are equal; returns **false** otherwise.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let rational = util.RationalNumber.createRationalFromString("3/4");
  let result = rationalNumber.equals(rational);
  ```


### getCommonDivisor<sup>8+</sup>

static getCommonDivisor​(number1: number,number2: number): number

Obtains the greatest common divisor of two specified integers.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| number1 | number | Yes| The first integer used to get the greatest common divisor.|
| number2 | number | Yes| The second integer used to get the greatest common divisor.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Greatest common divisor obtained.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let result = util.RationalNumber.getCommonDivisor(4,6);
  ```


### getNumerator<sup>8+</sup>

getNumerator​(): number

Obtains the numerator of this **RationalNumber** object.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Numerator of this **RationalNumber** object.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let result = rationalNumber.getNumerator();
  ```


### getDenominator<sup>8+</sup>

getDenominator​(): number

Obtains the denominator of this **RationalNumber** object.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Denominator of this **RationalNumber** object.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let result = rationalNumber.getDenominator();
  ```


### isZero<sup>8+</sup>

isZero​():boolean

Checks whether this **RationalNumber** object is **0**.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the value of this **RationalNumber** object is **0**; returns **false** otherwise.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let result = rationalNumber.isZero();
  ```


### isNaN<sup>8+</sup>

isNaN​(): boolean

Checks whether this **RationalNumber** object is a Not a Number (NaN).

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if this **RationalNumber** object is a NaN (the denominator and numerator are both **0**); returns **false** otherwise.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let result = rationalNumber.isNaN();
  ```


### isFinite<sup>8+</sup>

isFinite​():boolean

Checks whether this **RationalNumber** object represents a finite value.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if this **RationalNumber** object represents a finite value (the denominator is not **0**); returns **false** otherwise.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let result = rationalNumber.isFinite();
  ```


### toString<sup>8+</sup>

toString​(): string

Obtains the string representation of this **RationalNumber** object.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| string | Returns **NaN** if the numerator and denominator of this object are both **0**; returns a string in Numerator/Denominator format otherwise, for example, **3/5**.|

**Example**
  ```js
  let rationalNumber = new util.RationalNumber(1,2);
  let result = rationalNumber.toString();
  ```

## LruBuffer<sup>8+</sup>

### Attributes

**System capability**: SystemCapability.Utils.Lang

| Name| Type| Readable| Writable| Description|
| -------- | -------- | -------- | -------- | -------- |
| length | number | Yes| No| Total number of values in this buffer.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  pro.put(1,8);
  let result = pro.length;
  ```


### constructor<sup>8+</sup>

constructor(capacity?: number)

A constructor used to create an **LruBuffer** instance. The default capacity of the buffer is 64.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| capacity | number | No| Capacity of the **LruBuffer** to create.|

**Example**
  ```js
  let lrubuffer= new util.LruBuffer();
  ```


### updateCapacity<sup>8+</sup>

updateCapacity(newCapacity: number): void

Changes the **LruBuffer** capacity. If the new capacity is less than or equal to **0**, an exception will be thrown.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| newCapacity | number | Yes| New capacity of the **LruBuffer**.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  let result = pro.updateCapacity(100);
  ```


### toString<sup>8+</sup>

toString(): string

Obtains the string representation of this **LruBuffer** object.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| string | String representation of this **LruBuffer** object.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  pro.get(2);
  pro.remove(20);
  let result = pro.toString();
  ```


### getCapacity<sup>8+</sup>

getCapacity(): number

Obtains the capacity of this buffer.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Capacity of this buffer.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  let result = pro.getCapacity();
  ```


### clear<sup>8+</sup>

clear(): void

Clears key-value pairs from this buffer. The **afterRemoval()** method will be called to perform subsequent operations.

**System capability**: SystemCapability.Utils.Lang

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result = pro.length;
  pro.clear();
  ```


### getCreateCount<sup>8+</sup>

getCreateCount(): number

Obtains the number of return values for **createDefault()**.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Number of return values for **createDefault()**.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(1,8);
  let result = pro.getCreateCount();
  ```


### getMissCount<sup>8+</sup>

getMissCount(): number

Obtains the number of times that the queried values are mismatched.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Number of times that the queried values are mismatched.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  pro.get(2);
  let result = pro.getMissCount();
  ```


### getRemovalCount<sup>8+</sup>

getRemovalCount(): number

Obtains the number of removals from this buffer.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Number of removals from the buffer.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  pro.updateCapacity(2);
  pro.put(50,22);
  let result = pro.getRemovalCount();
  ```


### getMatchCount<sup>8+</sup>

getMatchCount(): number

Obtains the number of times that the queried values are matched.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Number of times that the queried values are matched.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  pro.get(2);
  let result = pro.getMatchCount();
  ```


### getPutCount<sup>8+</sup>

getPutCount(): number

Obtains the number of additions to this buffer.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| number | Number of additions to the buffer.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result = pro.getPutCount();
  ```


### isEmpty<sup>8+</sup>

isEmpty(): boolean

Checks whether this buffer is empty.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the buffer does not contain any value.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result = pro.isEmpty();
  ```


### get<sup>8+</sup>

get(key: K): V | undefined

Obtains the value of the specified key.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| key | K | Yes| Key based on which the value is queried.|

**Return value**

| Type| Description|
| -------- | -------- |
| V \| undefind | Returns the value of the key if a match is found in the buffer; returns **undefined** otherwise.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result  = pro.get(2);
  ```


### put<sup>8+</sup>

put(key: K,value: V): V

Adds a key-value pair to this buffer.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| key | K | Yes| Key of the key-value pair to add.|
| value | V | Yes| Value of the key-value pair to add.|

**Return value**

| Type| Description|
| -------- | -------- |
| V | Returns the existing value if the key already exists; returns the value added otherwise. If the key or value is null, an exception will be thrown. |

**Example**
  ```js
  let pro = new util.LruBuffer();
  let result = pro.put(2,10);
  ```

### values<sup>8+</sup>

values(): V[]

Obtains all values in this buffer, listed from the most to the least recently accessed.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| V [] | All values in the buffer, listed from the most to the least recently accessed.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  pro.put(2,"anhu");
  pro.put("afaf","grfb");
  let result = pro.values();
  ```


### keys<sup>8+</sup>

keys(): K[]

Obtains all keys in this buffer, listed from the most to the least recently accessed.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| K [] | All keys in the buffer, listed from the most to the least recently accessed.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result = pro.keys();
  ```


### remove<sup>8+</sup>

remove(key: K): V | undefined

Removes the specified key and its value from this buffer.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| key | K | Yes| Key to remove.|

**Return value**

| Type| Description|
| -------- | -------- |
| V \| undefind | Returns an **Optional** object containing the removed key-value pair if the key exists in the buffer; returns an empty **Optional** object otherwise. If the key is null, an exception will be thrown.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result = pro.remove(20);
  ```


### afterRemoval<sup>8+</sup>

afterRemoval(isEvict: boolean,key: K,value: V,newValue: V): void

Performs subsequent operations after a value is removed.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| isEvict | boolean | No| Whether the buffer capacity is insufficient. If the value is **true**, this method is called due to insufficient capacity.|
| key | K | Yes| Key removed.|
| value | V | Yes| Value removed.|
| newValue | V | No| New value for the key if the **put()** method is called and the key to be added already exists. In other cases, this parameter is left blank.|

**Example**
  ```js
  let arr = [];
  class ChildLruBuffer<K, V> extends util.LruBuffer<K, V>
  {
  	constructor()
  	{
  		super();
  	}
  	afterRemoval(isEvict, key, value, newValue)
  	{
  		if (isEvict === false)
  		{
  			arr = [key, value, newValue];
  		}
  	}
  }
  let lru = new ChildLruBuffer();
  lru.afterRemoval(false,10,30,null);
  ```


### contains<sup>8+</sup>

contains(key: K): boolean

Checks whether this buffer contains the specified key.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| key | K | Yes| Key to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the buffer contains the specified key; returns **false** otherwise.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result = pro.contains(20);
  ```


### createDefault<sup>8+</sup>

createDefault(key: K): V

Creates a value if the value of the specified key is not available.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| key | K | Yes| Key of which the value is missing.|

**Return value**

| Type| Description|
| -------- | -------- |
| V | Value of the key.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  let result = pro.createDefault(50);
  ```


### entries<sup>8+</sup>

entries(): IterableIterator&lt;[K,V]&gt;

Obtains a new iterator object that contains all key-value pairs in this object.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| [K, V] | Iterable array.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result = pro.entries();
  ```


### [Symbol.iterator]<sup>8+</sup>

[Symbol.iterator]\(): IterableIterator&lt;[K, V]&gt;

Obtains a two-dimensional array in key-value pairs.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| [K, V] | Two-dimensional array in key-value pairs.|

**Example**
  ```js
  let pro = new util.LruBuffer();
  pro.put(2,10);
  let result = pro[Symbol.iterator]();
  ```


## Scope<sup>8+</sup>


### ScopeType<sup>8+</sup>

Defines the type of values in a **Scope** object. The value type can be **ScopeComparable** or **number**.

The values of the **ScopeComparable** type are used to implement the **compareTo** method. Therefore, ensure that the input parameters are comparable.
```js
interface ScopeComparable{
    compareTo(other: ScopeComparable): boolean;
}
type ScopeType = ScopeComparable | number;
```


Create a class to implement the **compareTo** method. In the subsequent sample code, **Temperature** is used as an example of the [ScopeType](#scopetype8) object.


Example
```js
class Temperature{
    constructor(value){
       // If TS is used for development, add the following code:
       // private readonly _temp: Temperature;
       this._temp = value;
    }
    comapreTo(value){
       return this._temp >= value.getTemp();
    }
    getTemp(){
       return this._temp;
    }
    toString(){
       return this._temp.toString();
    }
}
```


### constructor<sup>8+</sup>

constructor(lowerObj: ScopeType, upperObj: ScopeType)

A constructor used to create a **Scope** object with the specified upper and lower limits.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| lowerObj | [ScopeType](#scopetype8) | Yes| Lower limit of the **Scope** object.|
| upperObj | [ScopeType](#scopetype8) | Yes| Upper limit of the **Scope** object.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let range = new util.Scope(tempLower, tempUpper);
  ```


### toString<sup>8+</sup>

toString(): string

Obtains a string representation that contains this **Scope**.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| string | String representation containing the **Scope**.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let range = new util.Scope(tempLower, tempUpper);
  let result = range.toString();
  ```


### intersect<sup>8+</sup>

intersect(range: Scope): Scope

Obtains the intersection of this **Scope** and the given **Scope**.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| range | [Scope](#scope8) | Yes| **Scope** specified.|

**Return value**

| Type| Description|
| -------- | -------- |
| [Scope](#scope8) | Intersection of this **Scope** and the given **Scope**.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let range = new util.Scope(tempLower, tempUpper);
  let tempMiDF = new Temperature(35);
  let tempMidS = new Temperature(39);
  let rangeFir = new util.Scope(tempMiDF, tempMidS);
  range.intersect(rangeFir );
  ```


### intersect<sup>8+</sup>

intersect(lowerObj:ScopeType,upperObj:ScopeType):Scope

Obtains the intersection of this **Scope** and the given lower and upper limits.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| lowerObj | [ScopeType](#scopetype8) | Yes| Lower limit.|
| upperObj | [ScopeType](#scopetype8) | Yes| Upper limit.|

**Return value**

| Type| Description|
| -------- | -------- |
| [Scope](#scope8) | Intersection of this **Scope** and the given lower and upper limits.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let tempMiDF = new Temperature(35);
  let tempMidS = new Temperature(39);
  let range = new util.Scope(tempLower, tempUpper);
  let result = range.intersect(tempMiDF, tempMidS);
  ```


### getUpper<sup>8+</sup>

getUpper(): ScopeType

Obtains the upper limit of this **Scope**.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| [ScopeType](#scopetype8) | Upper limit of this **Scope**.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let range = new util.Scope(tempLower, tempUpper);
  let result = range.getUpper();
  ```


### getLower<sup>8+</sup>

getLower(): ScopeType

Obtains the lower limit of this **Scope**.

**System capability**: SystemCapability.Utils.Lang

**Return value**

| Type| Description|
| -------- | -------- |
| [ScopeType](#scopetype8) | Lower limit of this **Scope**.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let range = new util.Scope(tempLower, tempUpper);
  let result = range.getLower();
  ```


### expand<sup>8+</sup>

expand(lowerObj: ScopeType,upperObj: ScopeType): Scope

Obtains the union set of this **Scope** and the given lower and upper limits.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| lowerObj | [ScopeType](#scopetype8) | Yes| Lower limit.|
| upperObj | [ScopeType](#scopetype8) | Yes| Upper limit.|

**Return value**

| Type| Description|
| -------- | -------- |
| [Scope](#scope8) | Union set of this **Scope** and the given lower and upper limits.|

**Example**

  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let tempMiDF = new Temperature(35);
  let tempMidS = new Temperature(39);
  let range = new util.Scope(tempLower, tempUpper);
  let result = range.expand(tempMiDF, tempMidS);
  ```


### expand<sup>8+</sup>

expand(range: Scope): Scope

Obtains the union set of this **Scope** and the given **Scope**.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| range | [Scope](#scope8) | Yes| **Scope** specified.|

**Return value**

| Type| Description|
| -------- | -------- |
| [Scope](#scope8) | Union set of this **Scope** and the given **Scope**.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let tempMiDF = new Temperature(35);
  let tempMidS = new Temperature(39);
  let range = new util.Scope(tempLower, tempUpper);
  let rangeFir = new util.Scope(tempMiDF, tempMidS);
  let result = range.expand(rangeFir);
  ```


### expand<sup>8+</sup>

expand(value: ScopeType): Scope

Obtains the union set of this **Scope** and the given value.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | [ScopeType](#scopetype8) | Yes| Value specified.|

**Return value**

| Type| Description|
| -------- | -------- |
| [Scope](#scope8) | Union set of this **Scope** and the given value.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let tempMiDF = new Temperature(35);
  let range = new util.Scope(tempLower, tempUpper);
  let result = range.expand(tempMiDF);
  ```


### contains<sup>8+</sup>

contains(value: ScopeType): boolean

Checks whether a value is within this **Scope**.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | [ScopeType](#scopetype8) | Yes| Value specified.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the value is within this **Scope**; returns **false** otherwise.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let tempMiDF = new Temperature(35);
  let range = new util.Scope(tempLower, tempUpper);
  range.contains(tempMiDF);
  ```


### contains<sup>8+</sup>

contains(range: Scope): boolean

Checks whether a range is within this **Scope**.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| range | [Scope](#scope8) | Yes| **Scope** specified.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the range is within this **Scope**; returns **false** otherwise.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let range = new util.Scope(tempLower, tempUpper);
  let tempLess = new Temperature(20);
  let tempMore = new Temperature(45);
  let rangeSec = new util.Scope(tempLess, tempMore);
  let result = range.contains(rangeSec);
  ```


### clamp<sup>8+</sup>

clamp(value: ScopeType): ScopeType

Limits a value to this **Scope**.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | [ScopeType](#scopetype8) | Yes| Value specified.|

**Return value**

| Type| Description|
| -------- | -------- |
| [ScopeType](#scopetype8) | Returns **lowerObj** if the specified value is less than the lower limit; returns **upperObj** if the specified value is greater than the upper limit; returns the specified value if it is within this **Scope**.|

**Example**
  ```js
  let tempLower = new Temperature(30);
  let tempUpper = new Temperature(40);
  let tempMiDF = new Temperature(35);
  let range = new util.Scope(tempLower, tempUpper);
  let result = range.clamp(tempMiDF);
  ```


## Base64<sup>8+</sup>


### constructor<sup>8+</sup>

constructor()

A constructor used to create a **Base64** object.

**System capability**: SystemCapability.Utils.Lang

**Example**
  ```js
  let base64 = new  util.Base64();
  ```


### encodeSync<sup>8+</sup>

encodeSync(src: Uint8Array): Uint8Array

Encodes the input content.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| src | Uint8Array | Yes| Uint8Array to encode.|

**Return value**

| Type| Description|
| -------- | -------- |
| Uint8Array | Uint8Array encoded.|

**Example**
  ```js
  let that = new util.Base64();
  let array = new Uint8Array([115,49,51]);
  let result = that.encodeSync(array);
  ```


### encodeToStringSync<sup>8+</sup>

encodeToStringSync(src: Uint8Array): string

Encodes the input content.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| src | Uint8Array | Yes| Uint8Array to encode.|

**Return value**

| Type| Description|
| -------- | -------- |
| string | String encoded from the Uint8Array.|

**Example**
  ```js
  let that = new util.Base64();
  let array = new Uint8Array([115,49,51]);
  let result = that.encodeToStringSync(array);
  ```


### decodeSync<sup>8+</sup>

decodeSync(src: Uint8Array | string): Uint8Array

Decodes the input content.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| src | Uint8Array \| string | Yes| Uint8Array or string to decode.|

**Return value**

| Type| Description|
| -------- | -------- |
| Uint8Array | Uint8Array decoded.|

**Example**
  ```js
  let that = new util.Base64();
  let buff = 'czEz';
  let result = that.decodeSync(buff);
  ```


### encode<sup>8+</sup>

encode(src: Uint8Array): Promise&lt;Uint8Array&gt;

Encodes the input content asynchronously.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| src | Uint8Array | Yes| Uint8Array to encode asynchronously.|

**Return value**

| Type| Description|
| -------- | -------- |
| Promise&lt;Uint8Array&gt; | Uint8Array obtained after asynchronous encoding.|

**Example**
  ```js
  let that = new util.Base64();
  let array = new Uint8Array([115,49,51]);
  let rarray = new Uint8Array([99,122,69,122]);
  that.encode(array).then(val=>{    
      for (var i = 0; i < rarray.length; i++) {        
          console.log(val[i].toString())
      }
  })
  ```


### encodeToString<sup>8+</sup>

encodeToString(src: Uint8Array): Promise&lt;string&gt;

Encodes the input content asynchronously.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| src | Uint8Array | Yes| Uint8Array to encode asynchronously.|

**Return value**

| Type| Description|
| -------- | -------- |
| Promise&lt;string&gt; | String obtained after asynchronous encoding.|

**Example**
  ```js
  let that = new util.Base64();
  let array = new Uint8Array([115,49,51]);
  that.encodeToString(array).then(val=>{    
      console.log(val)
  })
  ```


### decode<sup>8+</sup>

decode(src: Uint8Array | string): Promise&lt;Uint8Array&gt;

Decodes the input content asynchronously.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| src | Uint8Array \| string | Yes| Uint8Array or string to decode asynchronously.|

**Return value**

| Type| Description|
| -------- | -------- |
| Promise&lt;Uint8Array&gt; | Uint8Array obtained after asynchronous decoding.|

**Example**
  ```js
  let that = new util.Base64();
  let array = new Uint8Array([99,122,69,122]);
  let rarray = new Uint8Array([115,49,51]);
  that.decode(array).then(val=>{    
      for (var i = 0; i < rarray.length; i++) {        
          console.log(val[i].toString())
      }
  })
  ```


## types<sup>8+</sup>


### constructor<sup>8+</sup>

constructor()

A constructor used to create a **Types** object.

**System capability**: SystemCapability.Utils.Lang

**Example**
  ```js
  let type = new util.types();
  ```


### isAnyArrayBuffer<sup>8+</sup>

isAnyArrayBuffer(value: Object): boolean

Checks whether the input value is of the **ArrayBuffer** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **ArrayBuffer** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isAnyArrayBuffer(new ArrayBuffer(0));
  ```


### isArrayBufferView<sup>8+</sup>

isArrayBufferView(value: Object): boolean

Checks whether the input value is of the **ArrayBufferView** type.

**ArrayBufferView** is a helper type representing any of the following: **Int8Array**, **Int16Array**, **Int32Array**, **Uint8Array**, **Uint8ClampedArray**, **Uint32Array**, **Float32Array**, **Float64Array**, and **DataView**.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **ArrayBufferView** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isArrayBufferView(new Int8Array([]));
  ```


### isArgumentsObject<sup>8+</sup>

isArgumentsObject(value: Object): boolean

Checks whether the input value is of the **arguments** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **arguments** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  function foo() {
      var result = that.isArgumentsObject(arguments);
  }
  let f = foo();
  ```


### isArrayBuffer<sup>8+</sup>

isArrayBuffer(value: Object): boolean

Checks whether the input value is of the **ArrayBuffer** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **ArrayBuffer** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isArrayBuffer(new ArrayBuffer(0));
  ```


### isAsyncFunction<sup>8+</sup>

isAsyncFunction(value: Object): boolean

Checks whether the input value is an asynchronous function.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is an asynchronous function; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isAsyncFunction(async function foo() {});
  ```


### isBooleanObject<sup>8+</sup>

isBooleanObject(value: Object): boolean

Checks whether the input value is of the **Boolean** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Boolean** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isBooleanObject(new Boolean(true));
  ```


### isBoxedPrimitive<sup>8+</sup>

isBoxedPrimitive(value: Object): boolean

Checks whether the input value is of the **Boolean**, **Number**, **String**, or **Symbol** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Boolean**, **Number**, **String**, or **Symbol** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isBoxedPrimitive(new Boolean(false));
  ```


### isDataView<sup>8+</sup>

isDataView(value: Object): boolean

Checks whether the input value is of the **DataView** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **DataView** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  const ab = new ArrayBuffer(20);
  let result = that.isDataView(new DataView(ab));
  ```


### isDate<sup>8+</sup>

isDate(value: Object): boolean

Checks whether the input value is of the **Date** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Date** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isDate(new Date());
  ```


### isExternal<sup>8+</sup>

isExternal(value: Object): boolean

Checks whether the input value is of the **native external** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **native external** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isExternal(true);
  ```


### isFloat32Array<sup>8+</sup>

isFloat32Array(value: Object): boolean

Checks whether the input value is of the **Float32Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Float32Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isFloat32Array(new Float32Array());
  ```


### isFloat64Array<sup>8+</sup>

isFloat64Array(value: Object): boolean

Checks whether the input value is of the **Float64Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Float64Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isFloat64Array(new Float64Array());
  ```


### isGeneratorFunction<sup>8+</sup>

isGeneratorFunction(value: Object): boolean

Checks whether the input value is a generator function.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is a generator function; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isGeneratorFunction(function* foo() {});
  ```


### isGeneratorObject<sup>8+</sup>

isGeneratorObject(value: Object): boolean

Checks whether the input value is a generator object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is a generator object; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  function* foo() {}
  const generator = foo();
  let result = that.isGeneratorObject(generator);
  ```


### isInt8Array<sup>8+</sup>

isInt8Array(value: Object): boolean

Checks whether the input value is of the **Int8Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Int8Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isInt8Array(new Int8Array([]));
  ```


### isInt16Array<sup>8+</sup>

isInt16Array(value: Object): boolean

Checks whether the input value is of the **Int16Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Int16Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isInt16Array(new Int16Array([]));
  ```


### isInt32Array<sup>8+</sup>

isInt32Array(value: Object): boolean

Checks whether the input value is of the **Int32Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Int32Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isInt32Array(new Int32Array([]));
  ```


### isMap<sup>8+</sup>

isMap(value: Object): boolean

Checks whether the input value is of the **Map** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Map** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isMap(new Map());
  ```


### isMapIterator<sup>8+</sup>

isMapIterator(value: Object): boolean

Checks whether the input value is of the **MapIterator** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **MapIterator** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  const map = new Map();
  let result = that.isMapIterator(map.keys());
  ```


### isNativeError<sup>8+</sup>

isNativeError(value: Object): boolean

Checks whether the input value is of the **Error** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Error** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isNativeError(new TypeError());
  ```


### isNumberObject<sup>8+</sup>

isNumberObject(value: Object): boolean

Checks whether the input value is a number object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is a number object; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isNumberObject(new Number(0));
  ```


### isPromise<sup>8+</sup>

isPromise(value: Object): boolean

Checks whether the input value is a promise.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is a promise; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isPromise(Promise.resolve(1));
  ```


### isProxy<sup>8+</sup>

isProxy(value: Object): boolean

Checks whether the input value is a proxy.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is a proxy; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  const target = {};
  const proxy = new Proxy(target, {});
  let result = that.isProxy(proxy);
  ```


### isRegExp<sup>8+</sup>

isRegExp(value: Object): boolean

Checks whether the input value is of the **RegExp** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **RegExp** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isRegExp(new RegExp('abc'));
  ```


### isSet<sup>8+</sup>

isSet(value: Object): boolean

Checks whether the input value is of the **Set** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Set** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isSet(new Set());
  ```


### isSetIterator<sup>8+</sup>

isSetIterator(value: Object): boolean

Checks whether the input value is of the **SetIterator** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **SetIterator** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  const set = new Set();
  let result = that.isSetIterator(set.keys());
  ```


### isStringObject<sup>8+</sup>

isStringObject(value: Object): boolean

Checks whether the input value is a string object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is a string object; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isStringObject(new String('foo'));
  ```


### isSymbolObjec<sup>8+</sup>

isSymbolObject(value: Object): boolean

Checks whether the input value is a symbol object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is a symbol object; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  const symbols = Symbol('foo');
  let result = that.isSymbolObject(Object(symbols));
  ```


### isTypedArray<sup>8+</sup>

isTypedArray(value: Object): boolean

Checks whether the input value is of the **TypedArray** type.

**TypedArray** is a helper type representing any of the following: **Int8Array**, **Int16Array**, **Int32Array**, **Uint8Array**, **Uint8ClampedArray**, **Uint16Array**, **Uint32Array**, **Float32Array**, **Float64Array**, and **DataView**.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **TypedArray** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isTypedArray(new Float64Array([]));
  ```


### isUint8Array<sup>8+</sup>

isUint8Array(value: Object): boolean

Checks whether the input value is of the **Uint8Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Uint8Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isUint8Array(new Uint8Array([]));
  ```


### isUint8ClampedArray<sup>8+</sup>

isUint8ClampedArray(value: Object): boolean

Checks whether the input value is of the **Uint8ClampedArray** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Uint8ClampedArray** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isUint8ClampedArray(new Uint8ClampedArray([]));
  ```


### isUint16Array<sup>8+</sup>

isUint16Array(value: Object): boolean

Checks whether the input value is of the **Uint16Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Uint16Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isUint16Array(new Uint16Array([]));
  ```


### isUint32Array<sup>8+</sup>

isUint32Array(value: Object): boolean

Checks whether the input value is of the **Uint32Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **Uint32Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isUint32Array(new Uint32Array([]));
  ```


### isWeakMap<sup>8+</sup>

isWeakMap(value: Object): boolean

Checks whether the input value is of the **WeakMap** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **WeakMap** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isWeakMap(new WeakMap());
  ```


### isWeakSet<sup>8+</sup>

isWeakSet(value: Object): boolean

Checks whether the input value is of the **WeakSet** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **WeakSet** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isWeakSet(new WeakSet());
  ```


### isBigInt64Array<sup>8+</sup>

isBigInt64Array(value: Object): boolean

Checks whether the input value is of the **BigInt64Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **BigInt64Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isBigInt64Array(new BigInt64Array([]));
  ```


### isBigUint64Array<sup>8+</sup>

isBigUint64Array(value: Object): boolean

Checks whether the input value is of the **BigUint64Array** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **BigUint64Array** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isBigUint64Array(new BigUint64Array([]));
  ```


### isModuleNamespaceObject<sup>8+</sup>

isModuleNamespaceObject(value: Object): boolean

Checks whether the input value is a module namespace object.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is a module namespace object; returns **false** otherwise.|

**Example**
  ```js
  import url from '@ohos.url'
  let that = new util.types();
  let result = that.isModuleNamespaceObject(url);
  ```


### isSharedArrayBuffer<sup>8+</sup>

isSharedArrayBuffer(value: Object): boolean

Checks whether the input value is of the **SharedArrayBuffer** type.

**System capability**: SystemCapability.Utils.Lang

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | Object | Yes| Object to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the input value is of the **SharedArrayBuffer** type; returns **false** otherwise.|

**Example**
  ```js
  let that = new util.types();
  let result = that.isSharedArrayBuffer(new SharedArrayBuffer(0));
  ```