232.js

var MyQueue = function() {
    this.front=0; this.rear=-1;
    this.q = [];
};

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

/**
 * Removes the element from in front of queue and returns that element.
 * @return {number}
 */
MyQueue.prototype.pop = function() {
    let val = this.q[this.front];
    this.q[this.front] = undefined;
    this.front++;
    return val;
};

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

/**
 * Returns whether the queue is empty.
 * @return {boolean}
 */
MyQueue.prototype.empty = function() {
    return this.rear<this.front;
};