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How to use calculated properties in vue

亚连

Jun 22, 2018 pm 05:24 PM

vuevue.jsComputed properties

This article mainly introduces the use of vue computed properties and method examples of vue instances. The editor thinks it is quite good. Now I will share it with you and give it a reference. Let’s follow the editor and take a look.

This article introduces the use of vue calculated properties and examples of methods of vue instances. I would like to share them with you. The details are as follows:

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.

vue computed properties

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

The set/get method of calculated property:

<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>

Simple method of vue instance

vm is 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;);

is equivalent to:

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

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);

vm.$destroy -> Destroy the object

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

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

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