How Vue's keep-alive component optimizes image loading experience

Vue is a popular JavaScript framework that can help us build interactive web applications. During the development process, we often encounter situations where we need to load a large number of images, which often results in slower page loading and affects the user experience. This article will introduce how to use Vue’s keep-alive component to optimize the image loading experience.

Why do we need to optimize the image loading experience?

Pictures play a very important role in web pages, which can increase the attractiveness and readability of web pages and improve user experience. However, when a large number of images need to be loaded into the page, the browser needs to initiate multiple HTTP requests, which will cause the page response to slow down and the user to wait longer to see the complete page content. In addition, when users switch pages quickly, the loading of images may become chaotic and unable to keep up with the user's operation speed.

Use the keep-alive component to cache images

Vue’s keep-alive component is a very useful component that can help us cache components or pages that have been loaded. When optimizing the image loading experience, we can use the keep-alive component to cache already loaded images to improve the page's response speed.

First, we need to wrap the image that needs to be cached in a keep-alive component. For example, we have an image list component:

<template>
  <div>
    <img  src="/static/imghwm/default1.png"  data-src="image.url"  class="lazy"  v-for="image in images" : :key="image.id" / alt="How Vue's keep-alive component optimizes image loading experience" >
  </div>
</template>

<script>
export default {
  data() {
    return {
      images: [
        { id: 1, url: 'image1.jpg' },
        { id: 2, url: 'image2.jpg' },
        { id: 3, url: 'image3.jpg' },
        // ...
      ]
    };
  }
};
</script>

In order to optimize the image loading experience, we can wrap this component in a keep-alive component, as shown below:

<template>
  <div>
    <keep-alive>
      <img  src="/static/imghwm/default1.png"  data-src="image.url"  class="lazy"  v-for="image in images" : :key="image.id" / alt="How Vue's keep-alive component optimizes image loading experience" >
    </keep-alive>
  </div>
</template>

<script>
export default {
  data() {
    return {
      images: [
        { id: 1, url: 'image1.jpg' },
        { id: 2, url: 'image2.jpg' },
        { id: 3, url: 'image3.jpg' },
        // ...
      ]
    };
  }
};
</script>

By loading the image The list component is wrapped in a keep-alive component. We can ensure that the component will not be destroyed when switching pages, thereby avoiding reloading the image. When the user returns to the page again, the keep-alive component will directly obtain the loaded image from the cache to improve the page's response speed.

Solving the problem of cache invalidation

However, when using the keep-alive component to optimize the image loading experience, we also need to pay attention to a problem, that is, the cached images may become invalid after a period of time. When the user modifies the content of the image on other pages or adds a new image, the originally cached image may no longer be valid. To solve this problem, we can use a trigger to manually clear the image in the cache.

Suppose we have a trigger component to listen to the global picture change event:

<template>
  <div>
    <!-- 监听全局的图片变化事件 -->
    <img  src="/static/imghwm/default1.png"  data-src="@/assets/trigger.jpg"  class="lazy" @click="clearCache" / alt="How Vue's keep-alive component optimizes image loading experience" >
  </div>
</template>

<script>
export default {
  methods: {
    clearCache() {
      // 手动清除缓存中的图片
      this.$root.$emit('clearCache');
    }
  }
};
</script>

In the picture list component, we need to listen to the global picture change event and when the event is triggered Manually clear the images in the cache:

<template>
  <div>
    <!-- 监听全局的图片变化事件 -->
    <img  src="/static/imghwm/default1.png"  data-src="@/assets/trigger.jpg"  class="lazy" @click="clearCache" / alt="How Vue's keep-alive component optimizes image loading experience" >

    <keep-alive>
      <img  src="/static/imghwm/default1.png"  data-src="image.url"  class="lazy"  v-for="image in images" : :key="image.id" / alt="How Vue's keep-alive component optimizes image loading experience" >
    </keep-alive>
  </div>
</template>

<script>
export default {
  data() {
    return {
      images: [
        { id: 1, url: 'image1.jpg' },
        { id: 2, url: 'image2.jpg' },
        { id: 3, url: 'image3.jpg' },
        // ...
      ]
    };
  },
  mounted() {
    // 监听全局的图片变化事件
    this.$root.$on('clearCache', () => {
      // 手动清除缓存中的图片
      this.$refs.keepAlive.cache = {};
    });
  },
  beforeDestroy() {
    // 解绑事件
    this.$root.$off('clearCache');
  },
  methods: {
    clearCache() {
      // 触发全局的图片变化事件
      this.$root.$emit('clearCache');
    }
  }
};
</script>

In the above example, we mounted the instance of the keep-alive component to this.$refs by adding a ref attribute to the image list component. When listening to the click event of the trigger component, we can manually clear the images in the cache through the this.$refs.keepAlive.cache property.

Summary

By using Vue’s keep-alive component to cache already loaded images, we can significantly improve the image loading experience. At the same time, we also solved the cache invalidation problem by manually clearing the images in the cache to ensure that the cached images are always up to date.

The above is an introduction to the Vue keep-alive component on how to optimize the image loading experience. I hope it will be helpful to you!

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