Linear Container Deque
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 Deque from '@ohos.util.Deque';
System Capabilities
SystemCapability.Utils.Lang
Deque
Attributes
| Name | Type | Readable | Writable | Description |
|---|---|---|---|---|
| length | number | Yes | No | Number of entries in a double-ended queue (deque, called container later). |
constructor
constructor()
A constructor used to create a Deque instance.
Example
let deque = new Deque();
insertFront
insertFront(element: T): void
Inserts an entry at the front of this container.
Parameters
| Name | Type | Mandatory | Description |
|---|---|---|---|
| element | T | Yes | Entry to insert. |
Example
let deque = new Deque();
deque.insertFront("a");
deque.insertFront(1);
let b = [1, 2, 3];
deque.insertFront(b);
let c = {name : "lala", age : "13"};
deque.insertFront(false);
insertEnd
insertEnd(element: T): void
Inserts an entry at the end of this container.
Parameters
| Name | Type | Mandatory | Description |
|---|---|---|---|
| element | T | Yes | Entry to insert. |
Example
let deque = new Deque();
deque.insertEnd("a");
deque.insertEnd(1);
let b = [1, 2, 3];
deque.insertEnd(b);
let c = {name : "lala", age : "13"};
deque.insertEnd(false);
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 specified entry is contained; returns false otherwise. |
Example
let deque = new Deque();
let result = deque.has("Ahfbrgrbgnutfodgorrogorg");
deque.insertFront("Ahfbrgrbgnutfodgorrogorg");
let result1 = deque.has("Ahfbrgrbgnutfodgorrogorg");
popFirst
popFirst(): T
Removes the first entry of this container.
Return value
| Type | Description |
|---|---|
| T | Entry removed. |
Example
let deque = new Deque();
deque.insertFront(2);
deque.insertFront(4);
deque.insertEnd(5);
deque.insertFront(2);
deque.insertFront(4);
let result = deque.popFirst();
popLast
popLast(): T
Removes the last entry of this container.
Return value
| Type | Description |
|---|---|
| T | Entry removed. |
Example
let deque = new Deque();
deque.insertFront(2);
deque.insertEnd(4);
deque.insertFront(5);
deque.insertFront(2);
deque.insertFront(4);
let result = deque.popLast();
forEach
forEach(callbackfn: (value: T, index?: number, deque?: Deque<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 element that is currently traversed. |
| index | number | No | Position index of the entry that is currently traversed. |
| deque | Deque<T> | No | Instance that invokes the forEach method. |
Example
let deque = new Deque();
deque.insertFront(2);
deque.insertEnd(4);
deque.insertFront(5);
deque.insertEnd(4);
deque.forEach((value, index) => {
console.log("value:" + value, index);
});
getFirst
getFirst(): T
Obtains the first entry of this container.
Return value
| Type | Description |
|---|---|
| T | Entry obtained. |
Example
let deque = new Deque();
deque.insertEnd(2);
deque.insertEnd(4);
deque.insertFront(5);
deque.insertFront(4);
let result = deque.getFirst();
getLast
getLast(): T
Obtains the last entry of this container.
Return value
| Type | Description |
|---|---|
| T | Entry obtained. |
Example
let deque = new Deque();
deque.insertFront(2);
deque.insertFront(4);
deque.insertFront(5);
deque.insertFront(4);
let result = deque.getLast();
[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 deque = new Deque();
deque.insertFront(2);
deque.insertFront(4);
deque.insertFront(5);
deque.insertFront(4);
// Method 1:
for (let item of deque) {
console.log("value:" + item);
}
// Method 2:
let iter = deque[Symbol.iterator]();
let temp = iter.next().value;
while(temp != undefined) {
console.log("value:" + temp);
temp = iter.next().value;
}