computed，跟methods差不多，他是计算属性，能缓存
<!DOCTYPE html>
<html lang="en" xmlns:v-on="http://www.w3.org/1999/xhtml">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script src="http://cdn.bootcss.com/vue/2.1.6/vue.min.js"></script>
</head>
<body>
<div id="app">
<p>{{currentTime1()}}</p>
<p>{{currentTime2}}</p>
</div>
<script>
var vm = new Vue({
el: "#app", // 绑定元素，el是element的意思
data: {
msg: 'hello method'
},
methods: { //通过currentTime1()访问
currentTime1: function () {
return Date.now();
}
},
computed: { // 计算属性，通过currentTime2访问，有缓存
currentTime2: function () {
return Date.now();
}
}
});
</script>
</body>
</html>
