A computed property is that when the value of its dependent property changes, the value of this property will be automatically updated, and the DOM part related to it will also be updated automatically. Although inline expressions can be used to achieve very simple effects, it is inconvenient to use in complex scenarios. The most suitable use scenarios are simple Boolean operations or string concatenation. If more complex business logic is involved, you should preferably use computed properties.
The following is a direct comparison of three examples
- Use expressions directly to get values
<div id="app">
number1:<input type="text" v-model="num1"><br/>
number2:<input type="text" v-model="num2"><br/>
sumResu:<p>{{parseInt(num1)+parseInt(num2)}}</p>
</div>
<script>
Vue.config.productionTip=false;
var vm = new Vue({
el: '#app',
data: {
num1:10,
num2:20
},
});
</script>
- Expressions combined with methods to evaluate
<div id="app">
number1:<input type="text" v-model="num1"><br/>
number2:<input type="text" v-model="num2"><br/>
<!-- sumResu:<p>{{parseInt(num1)+parseInt(num2)}}</p> -->
sumResu:<p>{{Sum()}}</p>
</div>
<script>
Vue.config.productionTip=false;
var vm = new Vue({
el: '#app',
data: {
num1:10,
num2:20
},
methods: {
Sum(){
console.log(this)
return (+this.num1)+(+this.num2);
}
}
});
</script>
- Get value from computed property
<div id="app">
number1:<input type="text" v-model="num1"><br/>
number2:<input type="text" v-model="num2"><br/>
<!-- sumResu:<p>{{parseInt(num1)+parseInt(num2)}}</p> -->
<!-- sumResu:<p>{{Sum()}}</p> -->
sumResu:<p>{{sumResult}}</p>
</div>
<script>
Vue.config.productionTip=false;
var vm = new Vue({
el: '#app',
data: {
num1:10,
num2:20
},
methods: {
Sum(){
console.log(this)
return (+this.num1)+(+this.num2);
}
},
computed:{
sumResult:{
get(){
console.log(this);
return (+this.num1)+(+this.num2);
}
}
}
});
</script>
Summary: Computed properties have a caching mechanism, and the execution will only be triggered when the first execution and the value of the property it depends on changes; it can be abbreviated when the value is not changed.
Comments
Post a Comment