Skip to main content

Advantages of vue computed properties

 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.

Labels:

Comments

Post a Comment

Popular posts from this blog

Native ajax usage

 What is AJAX? AJAX stands for "Asynchronous Javascript And XML" (Asynchronous JavaScript and XML), which refers to a web development technology for creating interactive web applications for data interaction between browsers and servers. AJAX uses asynchronous data transfer (HTTP requests) between the browser and the web server, which allows web pages to request small amounts of information from the server instead of the entire page. AJAX describes a web application architecture that mainly uses scripts to manipulate HTTP. The main feature of AJAX applications is to use scripts to manipulate HTTP and web servers for data exchange without causing page reloads. Simply put, without reloading the entire web page, AJAX loads data in the background and displays it on the web page, which can partially refresh the page. The user has a better experience using the web page, but cannot go back.
Post a Comment
Read more

What is the difference between the box-size property content-box and border-box in the css box model?

 The box model is a very important concept in CSS layout, it includes content area, padding, border, and margin. Box models can be divided into two types: standard box models and IE box models. The box model, as the name suggests, is used to hold things, and the things it holds are the content of HTML elements. In other words, every visible HTML element is a box.
Post a Comment
Read more

vue routing global guard beforeEach and afterEach

 Global routing front guard (beforeEach) This function is used the most. Its function is to perform permission-related verification before routing jumps. This function contains three parameters: to: the object of the target route that is about to enter; from: the route that the current route is leaving; next: confirm the release. It can be used to log in and register, to determine whether there is a token before logging in, and release if it exists. , if it does not exist, it will not be released. The post routing guard (afterEach), its role is to trigger after the routing jump.
Post a Comment
Read more