How to deal with lazy loading of images in Vue technology development

How to handle lazy loading of images in Vue technology development

Lazy Loading is a commonly used web page optimization technology that can delay loading of images on the page. , thereby improving page loading speed and user experience. In Vue technology development, we can use some plug-ins or custom methods to implement lazy loading of images. This article will introduce the principle of lazy loading and specific code examples.

1. Principle of lazy loading

Normally, images in web pages are loaded from the beginning, while lazy loading delays the loading timing of images. The image will only start loading when it appears within the user's field of view. This can reduce the initial loading time of the page and improve user experience.

The principle of lazy loading is to use the browser's scrolling event and the characteristics of the document flow to determine whether to load the image by judging whether it is within the window. The specific implementation steps are as follows:

1. Set the src attribute of the image that needs to be loaded lazily to a placeholder image, such as a transparent 1-pixel image, or a base64-encoded image.
2. Listen to the browser's scroll event. When scrolling, traverse all the images in the page that need to be lazy loaded.
3. To determine whether the image is within the window, you can determine the position of the image by obtaining the offsetTop, offsetHeight of the image and the innerHeight of the window.
4. If the image is in the window, replace the src of the placeholder image with the actual image address and start loading the image.

2. Use the Vue plug-in to implement lazy loading of images

In the development of Vue technology, there are some ready-made plug-ins that can help us implement lazy loading of images, such as the vue-lazyload plug-in. The following is a specific code example:

1. Install the vue-lazyload plug-in

Use the npm or yarn command to install the vue-lazyload plug-in in the project:

npm install vue-lazyload

或

yarn add vue-lazyload

2. Introduce the vue-lazyload plug-in into main.js

import Vue from 'vue'
import VueLazyload from 'vue-lazyload'

Vue.use(VueLazyload)

3. Use the v-lazy instruction on images that need to be loaded lazily

<template>
  <img v-lazy="imageSrc" alt="图片">
</template>

Among them , imageSrc is the actual address of the image.

3. Customize instructions to implement lazy loading of images

In addition to using ready-made plug-ins, we can also customize instructions to implement lazy loading of images. The following is a simple code example of a custom directive:

1. Create a lazyload.js file and define the lazyload directive:

import Vue from 'vue'

Vue.directive('lazyload', {
  inserted: function(el) {
    function loadImage() {
      const rect = el.getBoundingClientRect()
      if (rect.top < window.innerHeight) {
        el.src = el.dataset.src
        el.removeAttribute('data-src')
        window.removeEventListener('scroll', loadImage)
      }
    }
    window.addEventListener('scroll', loadImage)
    loadImage()
  }
})

2. In main.js Introduce the lazyload instruction:

import Vue from 'vue'
import lazyload from './lazyload'

Vue.use(lazyload)

3. Use the v-lazyload instruction on images that need to be loaded lazily:

<template>
  <img v-lazyload="imageSrc" alt="图片">
</template>

Among them, imageSrc is the actual address of the image.

4. Summary

Lazy loading of images is a common technology to optimize web page loading speed and user experience. In Vue technology development, we can use ready-made plug-ins, such as vue-lazyload. To perform lazy loading, you can also customize instructions to implement the lazy loading function of images. The above is a detailed introduction and code examples on how to handle lazy loading of images in Vue technology development. I hope it will be helpful to your development work.

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