vuejs el-input实现textarea在光标处插入追加内容

html方法如下：
<el-input type="textarea" :autosize="{ minRows: 9 }" v-model="findings" id="findingsText"></el-input> //id不能少

js代码如下：
insertFindings(val) {
  const elInput = document.querySelector("#findingsText");
  const findingsStartPos = elInput.selectionStart;// 开始
  const findingsEndPos = elInput.selectionEnd; //结束
  const findings = this.findings.substring(0, findingsStartPos) + val + this.findings.substring(findingsEndPos);
  console.log('findings',findings)
}