一、props不为对象

 //子组件中不能修改props传入的值 会引发vue报错 一般在mounted之后将其值赋予新的变量
<template>
  <div>
    <p>I Am The Data Of Parent: {{ parentData }}</p>
    <child :childData="parentData "></child>
  </div>
</template>

<script>
  import Vue from 'vue';

  const child = Vue.extend({
    template: '<p>I Am The Data Of Child: {{ childData}}</p>',
    props: {
      childData: { type: String, required: true }
    },
    methods: {
      changeChildData() {
        setTimeout(() => {
           this.childData = 'newnewnew';
        }, 1000);
      }
    },
    mounted() {
      this.changeChildData();
    }
  });

export default {
  data() {
    return { parentData: 'oldoldold' };
  },
  methods: {
    changeParentData() {
      setTimeout(() => {
        this.parentData = 'pnewpnewpnew';
      }, 666);
    }
  },
  mounted() {
    this.changeParentData();
  },
  componts: { child }
};
</script>

当父组件修改props的值时子组件中值跟随改变；当子组件中值改变时 报错 且父组件值无变化；

二、props为对象

  //修改props传入对象属性即可 父组建属性跟随改变（ 同样不能直接修改整个对象 ）
<template>
  <div>
    <p>I Am The Data Of Parent: {{ parentData.data }}</p>
    <child :childData="parentData "></child>
  </div>
</template>

<script>
  import Vue from 'vue';

  const child = Vue.extend({
    template: '<p>I Am The Data Of Child: {{ childData.data }}</p>',
    props: {
      childData: { type: Object, required: true }
    },
    methods: {
      changeChildData() {
        setTimeout(() => {
           // this.childData = { **** }; error
           this.childData.data = 'newnewnew';
        }, 1000);
      }
    },
    mounted() {
      this.changeChildData();
    }
  });

export default {
  data() {
    return { parentData: { data: 'oldoldold' } };
  },
  methods: {
    changeParentData() {
      setTimeout(() => {
        // this.parentData = { **** };  run
        this.parentData.data = 'pnewpnewpnew';
      }, 666);
    }
  },
  mounted() {
    this.changeParentData();
  },
  componts: { child }
};
</script>

父子组件修改值时相互影响

建议props总是用对象；