How to solve the problem that the selected value does not change after changing the calculated attribute in Vue. The specific operations are as follows-JS Tutorial-php.cn

How to solve the problem that the selected value does not change after changing the calculated attribute in Vue. The specific operations are as follows

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Release： 2018-06-01 16:56:26

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Below I will share 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 start with 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: &#39;111&#39;,
      label: &#39;aaa&#39;
    }, {
      value: &#39;222&#39;,
      label: &#39;bbb&#39;
    }, {
      value: &#39;333&#39;,
      label: &#39;ccc&#39;
    }, {
      value: &#39;444&#39;,
      label: &#39;ddd&#39;
    }, {
      value: &#39;555&#39;,
      label: &#39;fff&#39;
    }];
    var vm = new Vue({
      el: &#39;#qwe&#39;,
      data: {
        options: [{
          value: &#39;选项1&#39;,
          label: &#39;黄金糕&#39;
        }, {
          value: &#39;选项2&#39;,
          label: &#39;双皮奶&#39;
        }, {
          value: &#39;选项3&#39;,
          label: &#39;蚵仔煎&#39;
        }, {
          value: &#39;选项4&#39;,
          label: &#39;龙须面&#39;
        }, {
          value: &#39;选项5&#39;,
          label: &#39;北京烤鸭&#39;
        }],
        selected: &#39;&#39;
      },
      computed: {
        da: function () {
          var _self = this;
          return _self.options.filter(function (item) {
            return +item.value.split(&#39;&#39;)[2] > 2;
          });
        }
      }
    })
  </script>
</body>
</html>

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The above code uses vue’s v-for instruction to bind data to generate options, but today we are learning to write When I suddenly discovered a problem, I bound the calculated attribute da to the v-for instruction, and then replaced the source data options. As a result, the calculated attribute da was correct, but the selected attribute did not change. 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, but the selected attribute It 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.

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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