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vue computed caching issue - Stack Overflow

三叔 2017-06-12 09:31:36

840

I read the official document says:

The difference between

computed and methods is that computed will be cached based on their dependencies. If the data cannot be changed, computed It will not be re-executed when refreshing, but methods will be executed every time.

But the examples I wrote are not like this (the examples I wrote are official examples).

html：

<p id="app">
    <p>{{methodsNow()}}</p>
    <p>{{computedNow}}</p>
</p>

javascript：

new Vue({
    el:'#app',
    data:{

    },
    methods:{
        methodsNow:function(){
            return new Date().toLocaleString();
        }
    },
    computed:{
        computedNow:function(){
            return new Date().toLocaleString();
        }
    }
});

Let’s discuss, did I write something wrong somewhere?

三叔

reply all(2)

三叔2017-06-12 09:33:36 2 floor

你的例子对于描述二者不同这点上，没有帮助。给你看这个例子：JSFiddle

new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue.js!'
  },
  methods:{
    methodsNow: function(){
      return new Date().toLocaleString();
    },
    showMethod: function() {
         alert(this.methodsNow());
    },
    showComputed: function() {
         alert(this.computedNow);
    }
  },
  computed:{
    computedNow: function(){
      return new Date().toLocaleString();
    }
  }
})

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扔个三星炸死你2017-06-12 09:33:36 1 floor

你这样测试下就明白了
html：


    
{{methodsNow()}}
    {{computedNow}}
    {{methodsNow()}}
    {{computedNow}}

javascript：

new Vue({
    el:'#app',
    data () {
      return {
        mData: 1,
        cData: 2
      }
    },
    methods: {
      methodsNow: function () {
        console.log('methods')
        return this.mData
      }
    },
    computed: {
      computedNow: function () {
        console.log('computed')
        return this.cData
      }
    }
});

结果你发现computedNow执行了一次，methodsNow执行了两次

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