Vue獲取textarea光標插入內容

<div style="background-color: #efefef; width:100%;height: 300px;">
  <textarea ref="contentArea" v-model="contentFormula"  style="width: 100%;height: 100%">
    {{contentFormula}}
  </textarea>
</div>

const myField = this.$refs.contentArea;
if (myField.selectionStart || myField.selectionStart === 0) {
  let startPos = myField.selectionStart;
  let endPos = myField.selectionEnd;
  this.contentFormula = myField.value.substring(0, startPos) + value + myField.value.substring(endPos, myField.value.length);
  this.$nextTick(()=>{
    myField.focus();
    myField.setSelectionRange(endPos + value.length, endPos + value.length)
  })
} else {
  this.contentFormula += value
}