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How to use calculated properties in vue

小云云

Dec 12, 2017 pm 01:07 PM

Instructions calculate

Computed properties

Expressions are very convenient in templates, but they are really only used for simple operations. Templates are used to describe the structure of views. Putting too much logic into a template can make it overweight and difficult to maintain. That's why Vue.js limits binding expressions to one expression. If the logic of more than one expression is required, computed properties should be used. This article mainly introduces the use of vue calculated attributes and method examples of vue instances. The editor thinks it is quite good. Now I will share it with you and give you a reference. I hope it can help everyone.

vue computed attribute

When we want to return the value of an attribute based on the execution result of one end of the business code, we can use the computed attribute computed,

Computed property is a function with results. It has get method and set method. The get method must have a return value and must have a return value

<script src="lib/vue.js"></script> 
 
<body> 
<p id="box"> 
  a = >{{a}} 
  b = > {{b}} 
</p> 
</body> 
<script> 
  var vm = new Vue({ 
    el:&#39;#box&#39;, 
    data:{ 
      a:1 
    }, 
    computed:{ 
      b:function () { 
        //业务代码 
        return this.a+1; 
      } 
    } 
  }); 
  /**这样直接改属性的值不行的，需要调用计算属性的set方法**/ 
  document.onclick = function(){ 
    vm.b = 3; 
  }; 
</script>

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Set/get method of calculated attribute:

<script src="lib/vue.js"></script> 
 
<body> 
<p id="box"> 
  a = >{{a}} 
  b = > {{b}} 
</p> 
</body> 
<script> 
  var vm = new Vue({ 
    el:&#39;#box&#39;, 
    data:{ 
      a:1 
    }, 
    computed:{ 
      b:{ 
        get:function () { 
          return this.a+1; 
        }, 
        set:function(val){ 
          this.a = val; 
        } 
      } 
    } 
  }); 
  /**这样直接改属性的值不行的，需要调用计算属性的set方法**/ 
  document.onclick = function(){ 
    vm.b = 3; 
    //默认调用计算属性的set方法 
  }; 
</script>

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Simple method of vue instance

vm Yes The name of the created vue instance object

vm.$el -> is the element

vm.$data -> is data

vm.$mount -> Mount the vue object on the node object

For example:

var vm2 = new Vue({ 
    data:{}, 
    methods:{} 
  }).$mount(&#39;#box&#39;);

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Equivalent to:

var vm2 = new Vue({ 
    el:&#39;#box&#39;, 
    data:{}, 
    methods:{} 
  });

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##vm.$options -> Get custom properties, custom methods

vue instances can customize properties and methods. If you need to call them, you need to call $options. For example:

var vm2 = new Vue({ 
   aa:&#39;1&#39;,//自定义属性 
   show:function () { 
     alert(1); 
   }, 
   el:&#39;#box&#39;, 
   data:{}, 
   methods:{} 
 }); 
 vm2.$options.show(); 
 console.log(vm2.$options.aa);

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vm.$destroy - > Destroy the object

##vm.$log(); -> Check the current status of the data

Related recommendations:

About Detailed explanation of the values of radio buttons, check buttons and drop-down lists in Vue.js form tags

Introduction to the implementation method of dividing components in Vue.js

Detailed analysis of several postures in Vue.js component communication

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