在input框的指定位置插入内容

this.question.gapQuestion?'':this.$set(this.question,'gapQuestion','')
      let oTxt1 = document.getElementById("gap");
      let cursurPosition=-1;
      if(oTxt1.selectionStart>=0){
        cursurPosition= oTxt1.selectionStart;
      }else{
        let range = document.selection.createRange();
        cursurPosition=range.text.length;
      }
      console.log(cursurPosition)
      this.question.gapQuestion = this.question.gapQuestion.slice(0,cursurPosition)+"______"+this.question.gapQuestion.slice(cursurPosition)
      oTxt1.selectionStart = cursurPosition
      oTxt1.selectionEnd = cursurPosition-5
      let gapArr = this.question.gapQuestion.split('______').length-1