How to use one Queue In Javascript

Using two Queues

In this approach, we will create a class and we will write the essential methods for implementation of the stack. as stack has pop, push, peek methods. we will going to build each method by crating a queue at first. stack and queue are opposite that’s why for FIFO and LIFO conditions we are adding some conditional statements.

Example: This example shows the implementation of the above-explained approach.

JavaScript

 class Stack {
     constructor() {
        this.queue = [];
     }

     push(value) {
        // Add new element to the end of the queue
        this.queue.push(value);

        // Rotate the queue so that the 
        // new element is at the front
        for (let i = 0; i < this.queue.length - 1; i++) {
          this.queue.push(this.queue.shift());
        }
      }

      pop() {
        if (this.isEmpty()) {
          return null; // Stack is empty
        }
        // Pop the top element from the
        // front of the queue
        return this.queue.shift(); 
      }

      peek() {
        if (this.isEmpty()) {
          return null;
        }
        // Return the front element of the queue
        return this.queue[0]; 
      }

      isEmpty() {
        return this.queue.length === 0;
      }

      clear(){
          let tempQueue = this.queue;
          this.queue = []; 
          return tempQueue;
      }
    }

    // Example usage
    const stack = new Stack();
    stack.push(1);
    stack.push(2);
    stack.push(3);
    console.log(stack.pop()); // Output: 3
    console.log(stack.peek()); // Output: 2
    console.log(stack);
    stack.clear(); 
    console.log(stack);

Output

3
2
2
1
Stack { queue: [] }
Stack { queue: [] }

Time complexity: O(n) for pushing elements into stack but other operation like ‘pop’, ‘peek’ have only 0( 1 ).

Space complexity: O(n) for storing elements in the stack. n is used for representing number of elements.

JavaScript program to implement stack using queue

In this article, we implement a JavaScript program to make a stack using a queue data structure. It provides essential stack methods like push(), pop(), and peek(), isEmpty() operations, utilizing either one or two queues to simulate the behavior of a stack.

Examples:

Input:
push(2)
push(3)
pop()
peek()
push(4)
isEmpty()

Output:
 3 2  false

Explanation:
push(2): The stack will be {2}
push(3): The stack will be {2 3}
pop():Pops last element (3), stack will be {2}
peek(): Peek top element of the stack 2
push(4): The stack will be {2 4}
isEmpty(): The stack is not empty so its "false".


Input:
push(1)
push(2)
push(3)
pop()
peek()
clear()

Output: 3 2 

Explanation:
push(1): The stack will be {1}
push(2): The stack will be {1,2}
push(3): The stack will be {1,2,3}
pop(): It pops last element (3), stack will be {1,2}
peek(): It peeks top element of the stack 2
clear() stack will be {}

These are the following approaches:

Table of Content

Using one Queue
Using two Queues

Tags:

#JavaScript-DSA #JavaScript #Web Technologies

Using two Queues

How to use one Queue In Javascript

JavaScript program to implement stack using queue

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