ImplementQueueusingStacks.js

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

/**
 * Push element x to the back of queue.
 * @param {number} x
 * @return {void}
 */
MyQueue.prototype.push = function(x) {
  this.stack.push(x)
  this.length = this.length + 1
};

/**
 * Removes the element from in front of queue and returns that element.
 * @return {number}
 */
MyQueue.prototype.pop = function() {
  let res = this.stack.shift()
  this.length = this.length - 1
  return res
};

/**
 * Get the front element.
 * @return {number}
 */
MyQueue.prototype.peek = function() {
  return this.stack[0]
};

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

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