js实现队列

方法一：利用两个栈实现队列

　　let stack1 = [], //两个数组模拟栈的行为
       stack2 = [];

    function push(node) {
        //栈是后入先出（LIFO），队列是先入先出（FIFO）
        while (stack2.length !== 0) {
            stack1.push(stack2.pop());
        }
        stack1.push(node);
    }

    function pop() {
        while (stack1.length !== 0) {
            stack2.push(stack1.pop());
        }
        return stack2.pop();
    }

    push(0);
    push(1);
    push(2);
    push(3);
    console.log(pop());
    console.log(pop());
    console.log(pop());
    console.log(pop());

方法二：

observal = {
   callback: [],
   add: function(node){
　    this.callback.push(node)
　},
　fire: function(){
   　this.callback.forEach(function(node){
        console.log(node);
    })
  }
}
observal.add(0);
observal.add(1);
observal.add(2);
observal.add(3); 
observal.fire();