JavaScript Exercises: N^th element from the top of the stack

JavaScript Stack: Exercise-16 with Solution

Write a JavaScript program to get the n^th element from the top of the stack.

Sample Solution:

JavaScript Code:

class Stack {
  constructor() {
    this.items = [];
  }
  push(element) {
    this.items.push(element);
  }
  pop() {
    if (this.isEmpty()) {
      return "Underflow";
    }
    return this.items.pop();
  }
  peek() {
    return this.items[this.items.length - 1];
  }
  isEmpty() {
    return this.items.length === 0;
  }
  size() {
    return this.items.length;
  }
getNthFromTop(n) {
    if (this.items.length < n) {
      return "Index out of range";
    }
    return this.items[this.items.length - n];
  }  
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();
 }      
}
let stack = new Stack();
stack.push(100);
stack.push(200);
stack.push(300);
stack.push(400);
stack.push(500);
stack.push(600);
stack.push(700);
console.log(stack.displayStack(stack));
n = 2;
console.log("nth element from the top of the stack where n = "+n);
console.log(stack.getNthFromTop(n));
n = 5;
console.log("nth element from the top of the stack where n = "+n);
console.log(stack.getNthFromTop(n));
n = 7;
console.log("nth element from the top of the stack where n = "+n);
console.log(stack.getNthFromTop(n));

Sample Output:

Stack elements are:
100 200 300 400 500 600 700
nth element from the top of the stack where n = 2
600
nth element from the top of the stack where n = 5
300
nth element from the top of the stack where n = 7
100

Flowchart:

Live Demo:

See the Pen javascript-stack-exercise-16 by w3resource (@w3resource) on CodePen.

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