stacks to queue

gistfile1.txt

function Queue(){
    var items = [];
    function Stack() {
        var item = [];
        this.push = function (elem) {
            item.push(elem);
            return item;
        };
        this.pop = function () {
            return item.pop();
        };
        this.isEmpty = function () {
            return item.length === 0;
        };
        this.get = function () {
            return item;
        };
    }
    var stack1 = new Stack();
    var stack2 = new Stack();
    this.push = function (elem) {
        stack1.push(elem);
        return items.push(elem);
    }
    this.pop = function () {
        if(stack1.isEmpty() && stack2.isEmpty()){
            throw new Error("空队列");
        }
        if(stack2.isEmpty() && !stack1.isEmpty()){
            while(!stack1.isEmpty()){
                stack2.push(stack1.pop());
            }
            return stack2.pop();
        }
    };
    this.get = function () {
        if(!stack2.isEmpty()){
            return stack2.get().reverse();
        }else{
            return items;
        }
    }
}
var queue = new Queue();
queue.push(0);
queue.push(1);
queue.push(2);
queue.get();
queue.pop();
queue.get();