js-apis-vector.md

# Linear Container Vector

> ![icon-note.gif](public_sys-resources/icon-note.gif) **NOTE**
> The initial APIs of this module are supported since API version 8. Newly added APIs will be marked with a superscript to indicate their earliest API version.


## Modules to Import

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

## System Capability

SystemCapability.Utils.Lang


## Vector


### Attributes

| Name| Type| Readable| Writable| Description|
| -------- | -------- | -------- | -------- | -------- |
| length | number | Yes| No| Number of entries in a vector (called container later).|


### constructor

constructor()

A constructor used to create a **Vector** instance.

**Example**

```
let vector = new Vector();
```


### add

add(element: T): boolean

Adds an entry at the end of this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Entry to add.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the entry is added successfully; returns **false** otherwise.|

**Example**

```
let vector = new Vector();
let result = vector.add("a");
let result1 = vector.add(1);
let b = [1, 2, 3];
vector.add(b);
let c = {name : "lala", age : "13"};
let result3 = vector.add(c);
```

### insert

insert(element: T, index: number): void

Inserts an entry at the specified position in this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Entry to insert.|
| index | number | Yes| Index of the position where the entry is to be inserted.|

**Example**

```
let vector = new Vector();
vector.insert("A", 0);
vector.insert(0, 1);
vector.insert(true, 2);
```

### has

has(element: T): boolean

Checks whether this container has the specified entry.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Entry to check.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the entry is contained; returns **false** otherwise.|

**Example**

```
let vector = new Vector();
let result = vector.has("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
vector.add("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
let result1 = vector.has("Ahfbrgrbgnutfodgorrogorgrogofdfdf");
``` 

### getIndexOf

getIndexOf(element: T): number

Obtains the index of the first occurrence of the specified entry in this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Entry to obtain.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Returns the position index if obtained; returns **-1** if the specified entry is not found.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(2);
vector.add(1);
vector.add(2);
vector.add(4);
let result = vector.getIndexOf(2);
```

### getLastIndexOf

getLastIndexOf(element: T): number

Obtains the index of the last occurrence of the specified entry in this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Entry to obtain.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Returns the position index if obtained; returns **-1** if the specified entry is not found.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(2);
vector.add(1);
vector.add(2);
vector.add(4);
let result = vector.getLastIndexOf(2);
```

### removeByIndex

removeByIndex(index: number): T

Removes an entry at the specified position from this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| index | number | Yes| Position index of the entry to remove.|

**Return value**

| Type| Description|
| -------- | -------- |
| T | Entry removed.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(2);
vector.add(4);
let result = vector.removeByIndex(2);
```

### remove

remove(element: T): boolean

Removes the first occurrence of the specified entry from this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Entry to remove.|

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the entry is removed successfully; returns **false** otherwise.|

**Return value**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.remove(2);
```

### removeByRange
removeByRange(fromIndex: number, toIndex: number): void;

Removes from this container all of the entries within a range, including the entry at the start position but not that at the end position.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| fromIndex | number | Yes| Index of the start position.|
| toIndex | number | Yes| Index of the end position.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.removeByRange(2,4);
vector.removeByRange(4,3);
vector.removeByRange(2,6);
```

### replaceAllElements
replaceAllElements(callbackfn: (value: T, index?: number, vector?: Vector<T>) => T,
thisArg?: Object): void

Replaces all entries in this container with new entries, and returns the new ones.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| callbackfn | function | Yes| Callback invoked for replacement.|
| thisArg | Object | No| Value to use when the callback is invoked.|

callbackfn

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | T | Yes| Value of the entry that is currently traversed.|
| index | number | No| Position index of the entry that is currently traversed.|
| vector | Vector<T> | No| Instance that invokes the **replaceAllElements** API.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.replaceAllElements((value, index) => {
  return value = 2 * value;
});
vector.replaceAllElements((value, index) => {
  return value = value - 2;
});
```

### forEach
forEach(callbackfn: (value: T, index?: number, vector?: Vector<T>) => void,
thisArg?: Object): void;

Uses a callback to traverse the entries in this container and obtain their position indexes.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| callbackfn | function | Yes| Callback invoked for replacement.|
| thisArg | Object | No| Value to use when the callback is invoked.|

callbackfn

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| value | T | Yes| Value of the entry that is currently traversed.|
| index | number | No| Position index of the entry that is currently traversed.|
| vector | Vector<T> | No| Instance that invokes the **forEach** API.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.forEach((value, index) => {
  console.log(value, index)
});

```

### sort
sort(comparator?: (firstValue: T, secondValue: T) => number): void

Sorts entries in this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| comparator | function | No| Callback invoked for sorting.|

comparator

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| firstValue | T | Yes| Previous entry.|
| secondValue | T | Yes| Next entry.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.sort(a, (b => a - b));
vector.sort(a, (b => b - a));
vector.sort();
```

### subVector
subVector(fromIndex: number, toIndex: number): Vector<T>

Obtains entries within a range in this container, including the entry at the start position but not that at the end position, and returns these entries as a new **Vector** instance.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| fromIndex | number | Yes| Index of the start position.|
| toIndex | number | Yes| Index of the end position.|

**Return value**

| Type| Description|
| -------- | -------- |
| Vector<T> | New **Vector** instance obtained.|

**Return value**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.subVector(2,4);
let result1 = vector.subVector(4,3);
let result2 = vector.subVector(2,6);

```

### clear
clear(): void

Clears all entries in this container and sets its length to **0**.

**Return value**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.clear();
```

### clone
clone(): Vector<T>

Clones this container and returns a copy. The modification to the copy does not affect the original instance.

**Return value**

| Type| Description|
| -------- | -------- |
| Vector<T> | New **Vector** instance obtained.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.clone();
```

### getCapacity
getCapacity(): number

Obtains the capacity of this container.

**Return value**

| Type| Description|
| -------- | -------- |
| number | Capacity obtained.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.getCapacity();
```

### convertToArray
convertToArray(): Array<T>

Converts this container into an array.

**Return value**

| Type| Description|
| -------- | -------- |
| Array<T> | Array obtained.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.convertToArray();
```

### isEmpty
isEmpty(): boolean

Checks whether this container is empty (contains no entries).

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Returns **true** if the container is empty; returns **false** otherwise.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.isEmpty();
```

### increaseCapacityTo
increaseCapacityTo(newCapacity: number): void

Increases the capacity of this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| newCapacity | number | Yes| New capacity.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.increaseCapacityTo(2);
vector.increaseCapacityTo(8);
```

### trimToCurrentLength
trimToCurrentLength(): void

Trims the capacity of this container into its current length.

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.trimToCurrentLength();
```

### toString

toString(): string

Uses commas (,) to concatenate entries in this container into a string.

**Return value**

| Type| Description|
| -------- | -------- |
| string | String obtained.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.toSting();
```

### copyToArray

copyToArray(array: Array<T>): void

Copies entries in this container into an array to overwrite elements of the same position indexes.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| array | Array<T> | Yes| Array to which the entries in the container will be copied.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let array = ["a", "b", "c", "d", "e", "f"];
let result = vector.copyToArray(array);
```

### getFirstElement

getFirstElement(): T

Obtains the first entry in this container.

**Return value**

| Type| Description|
| -------- | -------- |
| T | The first entry obtained.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.getFirstElement();
```

### getLastElement

getLastElement(): T

Obtains the last entry in this container.

**Return value**

| Type| Description|
| -------- | -------- |
| T | The last entry obtained.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
let result = vector.getLastElement();
```

### getLastIndexFrom

getLastIndexFrom(element: T, index: number): number

Searches for an entry backward from the specified position index and returns the position index of the entry.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Entry to query.|
| index | number | Yes| Position index where the search starts.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Returns the position index if obtained; returns **-1** if the entry is not found.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.add("a");
let result = vector.getLastIndexFrom(4,3);
```

### getIndexFrom

getIndexFrom(element: T, index: number): number

Searches for an entry forward from the specified position index and returns the position index of the entry.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| element | T | Yes| Entry to query.|
| index | number | Yes| Position index where the search starts.|

**Return value**

| Type| Description|
| -------- | -------- |
| number | Returns the position index if obtained; returns **-1** if the entry is not found.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.add("a");
let result = vector.getIndexFrom(4, 3);
```

### setLength
setLength(newSize: number): void

Sets a new length for this container.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| newSize | number | Yes| New length to set.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);
vector.setLength(8);
vector.setLength(2);
```

### get
get(index: number): T 

Obtains an entry at the specified position in this container.

**Parameters**

  | Name| Type| Mandatory| Description|
  | -------- | -------- | -------- | -------- |
  | index | number | Yes| Position index of the entry to obtain.|

**Return value**

  | Type| Description|
  | -------- | -------- |
  | T | Entry obtained.|

**Example**

  ```
  let vector = new Vector();
  vector.add(2);
  vector.add(4);
  vector.add(5);
  vector.add(4);
  let result = vector.get(2);
  ```
### set
set(index: number, element: T): T

Replaces an entry at the specified position in this container with a given entry.

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| index | number | Yes| Position index of the entry to replace.|
| element | T | Yes| Entry to be used for replacement.|

**Return value**

  | Type| Description|
  | -------- | -------- |
  | T | New entry.|

**Example**

  ```
  let vector = new Vector();
  vector.add(2);
  vector.add(4);
  vector.add(5);
  vector.add(4);
  let result = vector.set(2, "A");
  ```

### [Symbol.iterator]

[Symbol.iterator]\(): IterableIterator<T>


Obtains an iterator. Each item of the iterator is a JavaScript object.

**Return value**
| Type| Description|
| -------- | -------- |
| IterableIterator<T> | Iterator obtained.|

**Example**

```
let vector = new Vector();
vector.add(2);
vector.add(4);
vector.add(5);
vector.add(4);

// Method 1:
for (let item of vector) { 
  console.log(item); 
} 

// Method 2:
let iter = vector[Symbol.iterator]();
let temp = iter.next().value;
while(temp != undefined) {
  console.log(temp);
  temp = iter.next().value;
}
```