Stack.js

class Stack {
  //Initializing stack with an empty array
  constructor() {
    this.arr = [];
    var top = 0;
  }
  //push_back is used to push the elements in the stack
  push_back(num) {
    arr[top] = num;
    top++;
  }
  //peek is used to return the element which is on the top of stack
  peek() {
    return arr[top];
  }

  //pop returns the element which is at the top and also removes it from the stack
  pop() {
    if (this.isEmpty()) {
      console.log("UnderFlow");
      return 0;
    } else {
      var temp = arr[top];
      top--;
      console.log("One element has been removed from the stack");
      return temp;
    }
  }
  //isEmpty is used to check whether the stack is empty or not
  isEmpty() {
    if (top == 0) {
      return true;
    } else {
      return false;
    }
  }
  // print is used to print all the elements of the stack
  print() {
    var output = "";
    for (var i = 0; i < top; i++) {
      output += arr[i] + " ";
    }
    return output;
  }
  //size is used to return the size of the stack
  count() {
    return top;
  }
}
//Implementation

//Taking input from the user that how many values he/she wants to push into the stack
var input = prompt(
  "Enter the number of values you want to push into the stack"
);

var another_arr = []; //Declaring the array

input = parseInt(input);

for (var i = 0; i < input; i++) {
  //Taking array values as an input from the user
  another_arr[i] = prompt("Enter Element " + (i + 1));
}

/*I will be taking the value of input be 3 and array values as 56,75,24 for explanation. */
var input = 3;

const another_arr = [56, 75, 24];

//Making an object of the stack class
var mystack = new Stack();

//Checking whether the stack is empty or not by isEmpty()
if (mystack.isEmpty() == true) {
  console.log("The stack is empty right now");
} else {
  console.log("The stack has elements in it");
}

//We can check it by count() also but it will not return true or false
console.log("The size of the current stack is", mystack.count()); //It will print 0.

//Pushing elements in the stack
for (var i = 0; i < input; i++) {
  mystack.push_back(another_arr[i]);
}

//After pushing all the elements then mystack will be [56,75,24]

//Printing the new size of the array using count()
console.log("The new size of stack is ", count()); // It will print 3.

//Printing the stack with print()
console.log("The elements present in stack are ", mystack.print()); //It will print 56 75 24.

//Removing the topmost element from the stack by pop()
var removed_element = mystack.pop(); //This will return 24.

console.log("The element which is popped from the stack is ", removed_element); //It will print 24

//Printing the stack after removing the element using print()
console.log(
  "The elements present after removing one element in stack are ",
  mystack.print()
); //It will print 56 75