下边是vue的源码
var raf = inBrowser && window.requestAnimationFrame;
var waitForTransitionStart = raf
/* istanbul ignore next */
? function (fn) {
raf(function () {
raf(fn);
});
} : function (fn) {
setTimeout(fn, 50);
};
原文：http://www.cnblogs.com/chenxijywc/p/5377442.html