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vue implements select method without changing the selected value

小云云Original: 2018-03-03 11:02:084356browse

This article mainly shares with you an article that solves the problem that the selected value does not change after vue changes the calculated attribute. It has a good reference value and I hope it will be helpful to everyone. Let’s follow the editor to take a look, I hope it can help everyone.

First the code:

//...
<body>
  <p id="qwe">
    <select v-model="selected">
      <option v-for="item in da" :value="item.value">{{item.value}}</option>
    </select>
    <span>{{selected}}</span>
  </p>
  <script>
    var dt = [{
      value: '111',
      label: 'aaa'
    }, {
      value: '222',
      label: 'bbb'
    }, {
      value: '333',
      label: 'ccc'
    }, {
      value: '444',
      label: 'ddd'
    }, {
      value: '555',
      label: 'fff'
    }];
    var vm = new Vue({
      el: '#qwe',
      data: {
        options: [{
          value: '选项1',
          label: '黄金糕'
        }, {
          value: '选项2',
          label: '双皮奶'
        }, {
          value: '选项3',
          label: '蚵仔煎'
        }, {
          value: '选项4',
          label: '龙须面'
        }, {
          value: '选项5',
          label: '北京烤鸭'
        }],
        selected: ''
      },
      computed: {
        da: function () {
          var _self = this;
          return _self.options.filter(function (item) {
            return +item.value.split('')[2] > 2;
          });
        }
      }
    })
  </script>
</body>
</html>

The above code uses vue’s v-for instruction to bind data to generate options, but when I was learning to write today, I suddenly discovered a problem, which is about to calculate The attribute da is bound to the v-for instruction, and then the source data options are replaced. As a result, the calculated attribute of da is correct, but the selected attribute has not changed. That is to say, the text of the drop-down box on the page has not changed when it is not expanded, as shown below:

Here you can see that the option of the drop-down box has been updated. However, the selected attribute is not updated synchronously because it caches the last selected value.

I don’t know if the design here is reasonable, because I rarely use it this way.

But if there are problems, they must be solved. Add selected='' to the calculated attribute in computed, and reset the selected attribute every time the dependency is updated.

Related recommendations:

jQuery Gets the select value and clears the selected status

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