JavaScript Exercises: Implement a stack with push and pop operations

JavaScript Stack: Exercise-1 with Solution

Write a JavaScript program to implement a stack with push and pop operations. Find the top element of the stack and check if it is empty or not.

Sample Solution:

JavaScript Code:

class Stack {
  constructor() {
    this.items = [];
  }
  
  // Pushes an element onto the stack
  push(element) {
    this.items.push(element);
  }
  
  // Removes the top element from the stack and returns it
  pop() {
    if (this.items.length == 0)
      return "Underflow";
    return this.items.pop();
  }
  
  // Returns the top element of the stack
  peek() {
    if (this.items.length == 0)
      return "No elements in Stack";
    return this.items[this.items.length - 1];
  }
  
  // Checks if the stack is empty
  isEmpty() {
    return this.items.length == 0;
  }
 
  // Returns the number of elements in the stack
  size() {
    return this.items.length;
  }  
  
displayStack(stack) {
  console.log("Stack elements are:");
  let str = "";
  for (let i = 0; i < stack.items.length; i++)
    str += stack.items[i] + " ";
  return str.trim();
 }      
}
console.log("Initialize a stack:")
let stack = new Stack();
console.log("Is the stack empty?");
console.log(stack.isEmpty()); // true
console.log("Input some elements on the stack:")
stack.push(1);
stack.push(2);
stack.push(3);
stack.push(4);
stack.push(5);
console.log(stack.displayStack(stack));
console.log("Top of the element of the stack:");
console.log(stack.peek()); 
console.log("Size of the stack:");
console.log(stack.size()); 
console.log("Remove one element from the stack:")
stack.pop();
console.log(stack.displayStack(stack));
console.log("Top of the element of the stack:");
console.log(stack.peek());  
console.log("Is the stack empty?");
console.log(stack.isEmpty());
console.log("Size of the stack:");
console.log(stack.size());

Sample Output:

Initialize a stack:
Is the stack empty?
true
Input some elements on the stack:
Stack elements are:
1 2 3 4 5
Top of the element of the stack:
5
Size of the stack:
5
Remove one element from the stack:
Stack elements are:
1 2 3 4
Top of the element of the stack:
4
Is the stack empty?
false
Size of the stack:
4

Flowchart:

Live Demo:

See the Pen javascript-stack-exercise-1 by w3resource (@w3resource) on CodePen.

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