vue iview 最大字数动态显示textarea剩余字数

<FormItem label="留言内容">
  <Input
      v-model="form.content"
      :maxlength="maxlength"
      type="textarea"
      @input="descInput"
      :autosize="{ minRows: 5, maxRows: 8 }"
      placeholder="请输入留言"
  />
  <span>{{ remnant }}/{{maxlength}}</span>
</FormItem>

data() {
  return {
  form: {
    phone: "",
    content: "",
  },
  maxlength: 200,
  remnant: 200
  };
 },
 descInput() {
 let txtVal = this.form.content.length;
 this.remnant = this.maxlength - txtVal;
 },