1 var _timeoutIDIndex = 0;
 2 
 3 var TimeoutInfo = function TimeoutInfo(cb, delay, isRepeat, target, args) {
 4   _classCallCheck(this, TimeoutInfo);
 5 
 6   this.cb = cb;
 7   this.id = ++_timeoutIDIndex;
 8   this.start = performance.now();
 9   this.delay = delay;
10   this.isRepeat = isRepeat;
11   this.target = target;
12   this.args = args;
13 };
14 
15 var _timeoutInfos = {};
16 
17 function fireTimeout(nowMilliSeconds) {
18   var info;
19 
20   for (var id in _timeoutInfos) {
21     info = _timeoutInfos[id];
22 
23     if (info && info.cb) {
24       if (nowMilliSeconds - info.start >= info.delay) {
25         // console.log(`fireTimeout: id ${id}, start: ${info.start}, delay: ${info.delay}, now: ${nowMilliSeconds}`);
26         if (typeof info.cb === 'string') {
27           Function(info.cb)();
28         } else if (typeof info.cb === 'function') {
29           info.cb.apply(info.target, info.args);
30         }
31 
32         if (info.isRepeat) {
33           info.start = nowMilliSeconds;
34         } else {
35           delete _timeoutInfos[id];
36         }
37       }
38     }
39   }
40 }
41 
42 function createTimeoutInfo(prevFuncArgs, isRepeat) {
43   var cb = prevFuncArgs[0];
44 
45   if (!cb) {
46     console.error("createTimeoutInfo doesn't pass a callback ...");
47     return 0;
48   }
49 
50   var delay = prevFuncArgs.length > 1 ? prevFuncArgs[1] : 0;
51   var args;
52 
53   if (prevFuncArgs.length > 2) {
54     args = Array.prototype.slice.call(prevFuncArgs, 2);
55   }
56 
57   var info = new TimeoutInfo(cb, delay, isRepeat, this, args);
58   _timeoutInfos[info.id] = info;
59   return info.id;
60 }
61 
62 window.setTimeout = function (cb) {
63   return createTimeoutInfo(arguments, false);
64 };
65 
66 window.clearTimeout = function (id) {
67   delete _timeoutInfos[id];
68 };
69 
70 window.setInterval = function (cb) {
71   return createTimeoutInfo(arguments, true);
72 };
73 
74 window.clearInterval = window.clearTimeout;

 

可以看到, setTimeout和setInterval都是创建了一个TimeOutInfo. 然后存放在_timeoutInfos数组中

 

 

 执行了gameTick

function tick(nowMilliSeconds) {
  if (_firstTick) {
    _firstTick = false;

    if (window.onload) {
      var event = new Event('load');
      event._target = window;
      window.onload(event);
    }
  }

  fireTimeout(nowMilliSeconds);

  for (var id in _requestAnimationFrameCallbacks) {
    _oldRequestFrameCallback = _requestAnimationFrameCallbacks[id];

    if (_oldRequestFrameCallback) {
      delete _requestAnimationFrameCallbacks[id];

      _oldRequestFrameCallback(nowMilliSeconds);
    }
  }

  flushCommands();
}

function flushCommands() {
  if (next_index > 0) {
    gl._flushCommands(next_index, buffer_data, commandCount);

    next_index = 0;
    commandCount = 0;
  }
}