vue如何使用watch监听指定数据的变化_vue.js

                    
      +      =          
        

data() {    return {      check: false,      sign_img: "",      submit_flag: false'    }  },  computed: {    btnObj() {      const { sign_img, check } = this      return {        sign_img,        check      }    }  },  watch: {    btnObj: {      handler: function(newVal,oldVal) {        if(!!this.sign_img && this.check){          this.submit_flag = true          this.sign_flag = '1'        }else{          this.submit_flag = false          this.sign_flag = '0'        }      },      deep: true,      immediate: true    }  }