cocos creator setTimeout setInterval的实现

var _timeoutIDIndex = 0;

var TimeoutInfo = function TimeoutInfo(cb, delay, isRepeat, target, args) {
  _classCallCheck(this, TimeoutInfo);

  this.cb = cb;
  this.id = ++_timeoutIDIndex;
  this.start = performance.now();
  this.delay = delay;
  this.isRepeat = isRepeat;
  this.target = target;
  this.args = args;
};

var _timeoutInfos = {};

function fireTimeout(nowMilliSeconds) {
  var info;

  for (var id in _timeoutInfos) {
    info = _timeoutInfos[id];

    if (info && info.cb) {
      if (nowMilliSeconds - info.start >= info.delay) {
        // console.log(`fireTimeout: id ${id}, start: ${info.start}, delay: ${info.delay}, now: ${nowMilliSeconds}`);
        if (typeof info.cb === 'string') {
          Function(info.cb)();
        } else if (typeof info.cb === 'function') {
          info.cb.apply(info.target, info.args);
        }

        if (info.isRepeat) {
          info.start = nowMilliSeconds;
        } else {
          delete _timeoutInfos[id];
        }
      }
    }
  }
}

function createTimeoutInfo(prevFuncArgs, isRepeat) {
  var cb = prevFuncArgs[0];

  if (!cb) {
    console.error("createTimeoutInfo doesn't pass a callback ...");
    return 0;
  }

  var delay = prevFuncArgs.length > 1 ? prevFuncArgs[1] : 0;
  var args;

  if (prevFuncArgs.length > 2) {
    args = Array.prototype.slice.call(prevFuncArgs, 2);
  }

  var info = new TimeoutInfo(cb, delay, isRepeat, this, args);
  _timeoutInfos[info.id] = info;
  return info.id;
}

window.setTimeout = function (cb) {
  return createTimeoutInfo(arguments, false);
};

window.clearTimeout = function (id) {
  delete _timeoutInfos[id];
};

window.setInterval = function (cb) {
  return createTimeoutInfo(arguments, true);
};

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;
  }
}