//html
<div id="app1">
  <i>注意命名规定：仅在html内使用my-message</i>
  <child my-message="组件内部数据传递"></child>
</div>
//js
<script>
  Vue.component('child', {
    props: ['myMessage'],
    template: '<mark>{{ myMessage }}<mark/>'
  });
  new Vue({
    el: '#app1'
  })
</script>

<div id="app2">
  <input v-model="parentMsg">
  <br>
  <child :parent-msg="parentMsg"></child>
</div>
<script>
  Vue.component('child', {
    props: ['parentMsg'],
    template: '<mark>{{ parentMsg }}<mark/>'
  });
  new Vue({
    el: '#app2',
    data: {
      parentMsg: 'msg from parent!'
    }
  })
</script>

<comp some-prop="1"></comp>
//组件内部数据传递，对应字面量语法:传递了一个字符串"1" 

<comp v-bind:some-prop="1"></comp>
//组件与根节点数据传递，对应动态语法:传递实际的数字:js表达式 

//定义一个局部data属性，并将 prop 的初始值作为局部数据的初始值
props: ['initialCounter'],
    data: function () {
    return { counter: this.initialCounter }
    }
//定义一个局部computed属性，此属性从 prop 的值计算得出
 props: ['size'],
    computed: {
    normalizedSize: function () {
    return this.size.trim().toLowerCase()
    }
    }

<div id="parent">
<!-- vm.$refs.p will be the DOM node -->
<b ref="p">hello</b>
<!-- vm.$refs.child will be the child comp instance -->
<user-profile v-for='i in 3' ref="profile"></user-profile>
</div>
<script>
var userPf=Vue.component('user-profile',{
  template:'<div>hello $refs</div>'
});
var parent = new Vue({ el: '#parent' });
// 访问子组件
var child = parent.$refs.profile;
console.log(child[0]);
console.log(parent.$refs.p);
</script>

<div id="app3">
<p>Look at the parent's data: <mark>{{t}}</mark> & the child's data: <mark>{{childWords}}</mark></p>
<child v-on:add="pChange"></child>
<child v-on:add="pChange"></child>
<child v-on:click.native="native"></child>
</div>
<script>
Vue.component('child', {
  template: `<button @click="add">{{ c }}</button>`,
  data: function () {
    return {
      c: 0,
      msg: 'I am from child\'s data'
    }
  },
  methods: {
    add: function () {
      this.c += 1;
      this.$emit('add',this.msg);
    }
  },
});
new Vue({
  el: '#app3',
  data: {
    t: 0,
    childWords: ''
  },
  methods: {
    pChange: function (msg) {
      this.t += 1;
      this.childWords=msg;
    },
    native:function () {
      alert('I am a native event ,which comes from the root element！');
    }
  }
})
</script>

<div id="app4">
  <display></display>
  <increment></increment>
</div>
<script>
  var bus = new Vue();
  Vue.component('increment', {
    template: `<button @click="add">+</button>`,
    data: function () {
      return {count: 0}
    },
    methods: {
      add: function () {
        bus.$emit('inc', this.count+=1)
      }
    }
  });
  Vue.component('display', {
    template: `<span>Clicked: <mark>{{c}}</mark> times</span>`,
    data: function () {
      return {c: 0}
    },
    created: function () {
      var self=this;
//      bus.$on('inc', function (num) {
//        self.c = num
//      });
      bus.$on('inc', (num) =>
        this.c = num
      );
    }
  });
  vm = new Vue({
    el: "#app4",
  })
</script>