var Queue = function() {
this.list = [];
};
Queue.prototype = {
constructor: Queue,
queue: function(fn) {
this.list.push(fn)
return this;
},
wait: function(ms) {
this.list.push(ms)
return this;
},
dequeue: function() {
var self = this,
list = self.list;
self.isdequeue = true;
var el = list.shift() || function() {};
if (typeof el == "number") {
setTimeout(function() {
self.dequeue();
}, el);
} else if (typeof el == "function") {
el.call(this)
if (list.length) {
self.dequeue();
} else {
self.isdequeue = false;
}
}


}
};

var q = new Queue();

function a() {
console.log("a执行了", new Date());
}

function b() {
console.log("b执行了", new Date());
}
function c() {
console.log("c执行了", new Date());
}
function d() {
console.log("d执行了", new Date());
}
q.wait(2000);
q.queue(a);
q.wait(2000);
q.queue(b);
q.dequeue();


setTimeout(function(){//3S之后进来的
q.wait(2000);
q.queue(c);
},3000);

setTimeout(function(){//8S之后进来的
q.wait(2000);
q.queue(d);
q.dequeue();
},8000);

var q = new Queue();

function a() {
console.log("a执行了", new Date());
}

function b() {
console.log("b执行了", new Date());
}

function c() {
console.log("c执行了", new Date());
}

function d() {
console.log("d执行了", new Date());
}

q.wait(2000);
q.queue(a);
if (!q.isdequeue) {
q.dequeue();
}
q.wait(2000);
q.queue(b);
if (!q.isdequeue) {
q.dequeue();
}


setTimeout(function() { //3S之后进来的
q.wait(2000);
q.queue(c);
if (!q.isdequeue) {
q.dequeue();
}
}, 3000);

setTimeout(function() { //8S之后进来的
q.wait(2000);
q.queue(d);
if (!q.isdequeue) {
q.dequeue();
}
}, 8000);