微信小程序- textarea同步字数

效果图

.wxml

　<view>
    <view class="tit-main">
      请补充详细问题和意见
      <text class="tit-deputy currentWordNumber">(必填，{{currentWordNumber|0}}/{{max}})</text>
    </view>
    <view class="idea">
      <textarea name="bindTextAreaBlur" bindinput="getValueLength" show-confirm-bar='true' maxlength="{{max}}">   
      </textarea>
    </view>
　</view>

.js

data: {
    max: 300,
    param: {
      content: ''
    }
  },
getValueLength: function(e) {
    let _this = this
    let value = e.detail.value
    let len = parseInt(value.length)
    var param = this.data.param;
    param.content = value
    if (len > _this.data.max) return;
    this.setData({
      currentWordNumber: len,
      param: param
    })
  }