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.

Queue follows the principle of First In First Out (FIFO). It supports insertion of elements at the end and removal from the front of the queue. Queue is implemented based on the queue data structure.

Unlike Deque, which supports insertion and removal at both the ends, Queue supports insertion at one end and removal at the other end.

Recommended use case: Use Queue in FIFO scenarios.

Modules to Import

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

Queue

Attributes

System capability: SystemCapability.Utils.Lang

constructor

constructor()

A constructor used to create a Queue instance.

System capability: SystemCapability.Utils.Lang

Example

let queue = new Queue();

add

add(element: T): boolean

Adds an element at the end of this container.

System capability: SystemCapability.Utils.Lang

Parameters

Return value

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 element from this container.

System capability: SystemCapability.Utils.Lang

Return value

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 element of this container.

System capability: SystemCapability.Utils.Lang

Parameters

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 elements in this container and obtain their position indexes.

System capability: SystemCapability.Utils.Lang

Parameters

callbackfn

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.

System capability: SystemCapability.Utils.Lang

Return value

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;
}