Stack.js

/** Class representing a Stack. */

class Stack {

  constructor() {
    this._storage = {};
    this._length = 0;
  }
  /*
  * Adds a new value at the end of the stack
  */
  push(value) {
    if(value !== ''){
      this._storage[this._length] = value;
      this._length++;
    }
  }

  /*
  * Removes the value at the top of the stack and returns it
  */
  pop() {
    if(!this.isEmpty()){
      const value = this._storage[this._length - 1];
      delete this._storage[this._length - 1];
      this._length--;
      return value;
    }
  }
  /*
  * Returns the value at the top of the stack without removing it
  */
  peek() {
    if(!this.isEmpty()){
      return this._storage[this._length - 1];
    }
  }

  /*
  * Returns true if the stack is empty else false
  */
  isEmpty() {
    return this._length === 0;
  }
}

const stack = new Stack();

stack.push(5);
stack.peek();
stack.pop();
stack.isEmpty();