组件相当于函数，v-bind相当于给这个函数的形参title=“实参post.title”
<div id="app">
<blog-post v-for="post in posts" v-bind:key="post.id" v-bind:title="post.title" ></blog-post>
</div>
<script>
Vue.component('blog-post',{
props: ['title'],
template: '<h3>{{ title }}</h3>'
});
var vm=new Vue({
el: '#blog-post-demo',
data: {
posts: [ { id: 1, title: 'My journey with Vue' }, { id: 2, title: 'Blogging with Vue' }, { id: 3, title: 'Why Vue is so fun' } ]
}})
</script>