vue入门第5天：子组件怎么能不改变父组件传过来的对象

父组件：app.vue

<el-header>
      <sucaiheader :testData='copyDataT'></sucaiheader>
    </el-header>

<script>
    import sucaiheader from "components/sucaiHeader.vue";
    export default {
        name: "homePage",
        data() {
            return {
                mianbaoxie: {
                    id:'1',
                    text:'居然跟传字符串不一样'
                },
                copyDataT:''
            }
        },
        methods:{
            copyData(){
              var mianbaoxie = JSON.parse(JSON.stringify(this.mianbaoxie))
                return mianbaoxie;
            }
        },
        created(){
           this.copyDataT=  this.copyData()
        },
        components:{
            sucaiheader,
        },

    };
</script>