## 傳值 父組?件通過屬性的方式向子組件傳遞數據. vue中有單向數據流的概念,父組件可以向子組件傳值,子組件只能去用這個數據,但是不要去修改父組件傳遞過來的值. 子組件通過this.$emit()向父組件傳值. ``` <div id="app"> <counter :number="1" @change="add"></counter> <counter :number="1" @change="add"></counter> {{total}} </div> <script> var counter = { props: ['number'], data: function () { return { n: this.number, }; }, template: ` <div> {{n}} <input type="button" value="add" @click="add"> </div> `, methods: { add: function () { this.n += this.number; this.$emit('change', 1); } } }; new Vue({ el: '#app', data: { total: 2, }, components: { counter, }, methods: { add: function (value) { this.total += value; } } }) </script> ```