Linear Container Stack

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 Stack from '@ohos.util.Stack';

System Capabilities

SystemCapability.Utils.Lang

Stack

Attributes

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

constructor

constructor()

A constructor used to create a Stack instance.

Example

let stack = new Stack();

push

push(item: T): T

Adds an entry at the top of this container.

Parameters

Name Type Mandatory Description
item T Yes Element to add.

Return value

Type Description
T Element added.

Example

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

pop

pop(): T

Removes the top entry from this container.

Return value

Type Description
T Entry removed.

Example

let stack = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(2);
stack.push(4);
let result = stack.pop();

peek

peek(): T

Obtains the top entry of this container.

Return value

Type Description
T Entry obtained.

Example

let stack = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(2);
let result = stack.peek();

locate

locate(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 query.

Return value

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

Example

let stack = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(2);
let result = stack.locate(2);

forEach

forEach(callbackfn: (value: T, index?: number, stack?: Stack<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.
stack Stack<T> No Instance that invokes the forEach method.

Example

let stack = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(4);
stack.forEach((value, index) => {
 console.log("value:" + value, index);
});

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 stack = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(4);
let result = stack.isEmpty();

[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 stack = new Stack();
stack.push(2);
stack.push(4);
stack.push(5);
stack.push(4);

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

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