ImplementStackusingQueues.js

/**
 * Initialize your data structure here.
 */
var MyStack = function() {
  this.stack = []
  this.length = 0;
};

/**
 * Push element x onto stack.
 * @param {number} x
 * @return {void}
 */
MyStack.prototype.push = function(x) {
  this.stack.push(x)
  this.length = this.length + 1
};

/**
 * Removes the element on top of the stack and returns that element.
 * @return {number}
 */
MyStack.prototype.pop = function() {
  let res = this.stack.pop()
  this.length = this.length - 1
  return res
};

/**
 * Get the top element.
 * @return {number}
 */
MyStack.prototype.top = function() {
  return this.stack[this.stack.length - 1]
};

/**
 * Returns whether the stack is empty.
 * @return {boolean}
 */
MyStack.prototype.empty = function() {
  if (this.length === 0) {
    return true
  } else {
    return false
  }
};

/**
 * Your MyStack object will be instantiated and called as such:
 * var obj = Object.create(MyStack).createNew()
 * obj.push(x)
 * var param_2 = obj.pop()
 * var param_3 = obj.top()
 * var param_4 = obj.empty()
 */