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How to achieve page preloading effect with keep-alive component in vue

WBOYOriginal: 2023-07-21 19:29:231571browse

How to achieve the page preloading effect of the keep-alive component in Vue

In Vue development, we often encounter the situation of frequently switching pages. At this time, if the component is re-rendered every time the page is switched, not only This will cause the page to load slower, and some requested data may be lost. In order to solve this problem, Vue provides a very practical component-keep-alive, which can cache components and achieve page preloading effect.

The keep-alive component is an abstract component built into Vue. It can cache dynamically switched components so that they can be used directly the next time they are needed. By using the keep-alive component, we can achieve the effect of retaining already loaded components when switching routes, avoiding repeated rendering and re-requesting data. Next, we will explain in detail how to use the keep-alive component to achieve the page preloading effect.

First, we need to install Vue and create a Vue project. You can use the Vue CLI or directly introduce a Vue script in an HTML file to create a Vue instance. In the following examples, we assume that Vue has been installed and a root instance created.

<!DOCTYPE html>
<html>
<head>
  <title>Vue Keep-alive Demo</title>
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
  <div id="app">
    <button @click="changePage">切换页面</button>
    <keep-alive>
      <component :is="currentPage"></component>
    </keep-alive>
  </div>

  <script>
    // 创建组件A
    const ComponentA = {
      template: '<div>组件A</div>',
      created() {
        console.log('组件A被创建了');
      }
    };

    // 创建组件B
    const ComponentB = {
      template: '<div>组件B</div>',
      created() {
        console.log('组件B被创建了');
      }
    };

    // 创建Vue实例
    new Vue({
      el: '#app',
      data() {
        return {
          currentPage: 'ComponentA'
        };
      },
      methods: {
        changePage() {
          this.currentPage = this.currentPage === 'ComponentA' ? 'ComponentB' : 'ComponentA';
        }
      },
      components: {
        ComponentA,
        ComponentB
      }
    });
  </script>
</body>
</html>

In the above example, we created two components ComponentA and ComponentB, and added a currentPage attribute to the data attribute of the root instance to mark the currently displayed component. In the button click event, we switch the displayed component by changing the value of the currentPage property.

Inside the keep-alive component, we use dynamic components to render the current component. It should be noted that when using the keep-alive component, we need to wrap the component that needs to be cached inside the keep-alive component and render the current component through a dynamic component. In this way, every time you switch a component, Vue will automatically cache the component before switching. The next time you switch to the same component, the cached component will be used directly without re-rendering.

In this example, we output the logs of component creation in the create hook functions of ComponentA and ComponentB respectively. We can click the button to switch to component A and component B respectively, and then switch back to the previous component. Observe the output of the browser console. We can find that when switching back to the previous component, the created hook function is not triggered, indicating that the component is cached. Woke up.

Through the above example, we can see how to use the keep-alive component to achieve the preloading effect of the page. Using keep-alive components can avoid repeated rendering of components and re-requesting data, improving page loading speed and user experience.

However, it should be noted that keep-alive is not a panacea. For some components that need to update data in real time, or for some components that already contain user interaction logic, we may not want to cache them. In this case, we can specify the components that do not need to be cached by configuring the exclude attribute of the keep-alive component.

To sum up, using keep-alive components can simplify the development of Vue projects and improve page loading speed and user experience. However, the keep-alive component needs to be configured and used correctly according to the actual situation to achieve the best results. I hope the above introduction can help everyone understand and use the keep-alive component.

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