//作者：郅慧芳 
//來源：CSDN 
//原文：https://blog.csdn.net/qq_24612793/article/details/81283500 

<div class="applyInput cb mt3">
    <textarea placeholder="請(qǐng)輸入" maxlength="100" @input="descInput" v-model="desc" />
    <span class="numberV">{{txtVal}}/100</span>
 </div>

<script>
export default {
  name: 'applyAgent',
  data () {
    return {
      txtVal: 0,
      desc:""
    }
  },
  methods: {
    descInput(){
        this.txtVal = this.desc.length;
        }
    }
}
</script>

效果圖:

txtlength.png