<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>生命周期</title>
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
<div id='app'></div>
<script>
let app = new Vue({
el: '#app',
data: {
a: 1
},
created: function () {
// `this` 指向 vm 实例
console.log('a is: ' + this.a)
}
})
/*
不要在选项属性或回调上使用箭头函数，比如 created: () => console.log(this.a) 或 vm.$watch('a', newValue => this.myMethod())。
因为箭头函数并没有 this，this 会作为变量一直向上级词法作用域查找，直至找到为止，
经常导致 Uncaught TypeError: Cannot read property of undefined
或 Uncaught TypeError: this.myMethod is not a function 之类的错误
*/
</script>
</body>
</html>
