在实现倒计时功能时，遇到一个报错：

setTimeout expects a function as first argument but got undefined.;at pages/limited-sale/limited-sale onReady function;at setTimeout callback function
TypeError: setTimeout expects a function as first argument but got undefined.

打印了下，结果看到函数是undefined的

一看就知道这是this的指向问题了，将关键代码的定时器部分加下绑定就可以了：

this.timer = setTimeout(this.onTimeUp.bind(this), 1000)