Linear Container Queue

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 Queue from '@ohos.util.Queue';

System Capabilities

SystemCapability.Utils.Lang

Queue

Attributes

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

constructor

constructor()

A constructor used to create a Queue instance.

Example

let queue = new Queue();

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

pop

pop(): T

Removes the first entry from this container.

Return value

Type	Description
T	Entry removed.

Example

let queue = new Queue();
queue.add(2);
queue.add(4);
queue.add(5);
queue.add(2);
queue.add(4);
let result = queue.pop();

getFirst

getFirst(): T

Obtains the first entry of this container.

Parameters

Type	Description
T	The first entry obtained.

Example

let queue = new Queue();
queue.add(2);
queue.add(4);
queue.add(5);
queue.add(2);
let result = queue.getFirst();

forEach

forEach(callbackfn: (value: T, index?: number, Queue?: Queue<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 to traverse the entries in the container.
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.
Queue	Queue<T>	No	Instance that invokes the forEach method.

Example

let queue = new Queue();
queue.add(2);
queue.add(4);
queue.add(5);
queue.add(4);
queue.forEach((value, index) => {
  console.log("value:" + value, index);
});

[Symbol.iterator]

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

Obtains an iterator, each item of which is a JavaScript object.

Return value

Type	Description
IterableIterator<T>	Iterator obtained.

Example

let queue = new Queue();
queue.add(2);
queue.add(4);
queue.add(5);
queue.add(4);

// Method 1:
for (let item of queue) { 
  console.log("value:" + item); 
}

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