# String Encoding and Decoding >![](../../public_sys-resources/icon-note.gif) **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. ## Modules to Import ``` import util from '@ohos.util'; ``` ## Required Permissions None ## util.printf printf\(format: string, ...args: Object\[\]\): string Prints the input content in a formatted string. - Parameters

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

- Return values

Type	Description
string	String in the specified format.

- Example ``` var res = util.printf("%s", "hello world!"); console.log(res); ``` ## util.getErrorString getErrorString\(errno: number\): string Obtains detailed information about a system error code. - Parameters

Name	Type	Mandatory	Description
errno	number	Yes	Error code generated.

- Return values

Type	Description
string	Detailed information about the error code.

- Example ``` var errnum = 10; // 10: a system error number var 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 \(if the promise has been resolved, the value is **null**\), and the second parameter indicates the resolved value. - Parameters

Name	Type	Mandatory	Description
original	Function	Yes	Asynchronous function.

- Return values

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 ``` async function promiseFn() { return Promise.reject('value'); } var cb = util.callbackWrapper(promiseFn); cb((err, ret) => { expect(err).strictEqual('value'); expect(ret).strictEqual(undefined); }) ``` ## util.promiseWrapper promiseWrapper\(original: \(err: Object, value: Object\) =\> void\): Object Processes an asynchronous function and returns a promise version. - Parameters

Name	Type	Mandatory	Description
original	Function	Yes	Asynchronous function to process.

- Return values

Type	Description
Function	Function in the common error-first style (that is, (err, uses value) =>... is used as the last parameter) and the promise version.

- Example ``` function aysnFun(str1, str2, callback) { if (typeof str1 === 'string' && typeof str1 === 'string') { callback(null, str1 + str2); } else { callback('type err'); } } let newPromiseObj = util.promiseWrapper(aysnFun)("Hello", 'World'); newPromiseObj.then(res => { expect(res).strictEqual('HelloWorld'); }) ``` ## TextDecoder ### Attributes

Name	Type	Readable	Writable	Description
encoding	string	Yes	No	Encoding format. 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.

Name

Type

Readable

Writable

Description

encoding

string

Yes

Encoding format.

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

Whether to display fatal errors.

ignoreBOM

boolean

Yes

Whether to ignore the byte order marker (BOM). The default value is false.

### constructor constructor\(encoding?: string, options?: \{ fatal?: boolean; ignoreBOM?: boolean \},\) A constructor used to create a **TextDecoder** instance. - 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 ``` var textDecoder = new util.TextDecoder("utf-8",{ignoreBOM:true}); ``` ### decode decode\(input: Uint8Array, options?:\{stream?:false\}\): string Decodes the input parameters and outputs the text. - 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 the subsequent decode(). Set this parameter to true if data blocks are processed. If data is not divided into blocks or the last data block is processed, set this parameter to false. The default value is false.

- Return values

Type	Description
string	Data decoded.

- Example ``` var textDecoder = new util.TextDecoder("utf-8",{ignoreBOM:true}); var 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:"); for(var j= 0; j < 6; j++) { console.log(result[j]); } var retStr = textDecoder.decode( result , {stream:false}); console.log("retStr = " + retStr); ``` ## TextEncoder ### Attributes

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

### constructor constructor\(\) A constructor used to create a **TextEncoder** instance. - Example ``` var textEncoder = new util.TextEncoder(); ``` ### encode encode\(input?: string\): Uint8Array Encodes the input parameter. - Parameters

Name	Type	Mandatory	Description
input	string	Yes	String to encode.

- Return values

Type	Description
Uint8Array	Encoded text.

- Example ``` var textEncoder = new util.TextEncoder(); var result = new Uint8Array(buffer); result = textEncoder.encode("\uD800¥¥"); ``` ### encodeInto encodeInto\(input: string, dest: Uint8Array,\):\{ read: number; written: number \} Stores the UTF-8 encoded text. - 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 values

Type	Description
Uint8Array	Encoded text.

- Example ``` var that = new util.TextEncoder(); var buffer = new ArrayBuffer(4); this.dest = new Uint8Array(buffer); var result = that.encodeInto("abcd", this.dest); ```