JavaScript Data Structure - Deque

deque.js

var Deque = function() {
    this.arr = [];
};

Deque.prototype.size = function() {
    return this.arr.length;
};

Deque.prototype.empty = function() {
    return this.size() === 0;
};

Deque.prototype.push_front = function(val) {
    this.arr.unshift(val);
};

Deque.prototype.push_back = function(val) {
    this.arr.push(val);
};

Deque.prototype.pop_front = function() {
    return !this.empty() ? this.arr.shift() : -1;
};

Deque.prototype.pop_back = function() {
    return !this.empty() ? this.arr.pop() : -1;
};

Deque.prototype.front = function() {
    return !this.empty() ? this.arr[0] : -1;
};
Deque.prototype.back = function() {
    return !this.empty() ? this.arr[this.size()-1] : -1;
};