使用this.$set

    this.bSubmitIsSucc = this.$store.state.bIsSubmitSucc;
    this.axamList = JSON.parse(this.getAxamTopic);
    this.axamList.result.topicList.map((item) => {
     this.$set(item,"total",0)
      item.topicQuestions.map((obj) => {
        this.$set(obj, "isTrue", "");
        // this.total += obj.questionScore
      });
      
    });