Vue-Lazyload

Vue module for lazyloading images in your applications. Some of goals of this project worth noting include:

• Be lightweight, powerful and easy to use
• Work on any image type
• Add loading class while image is loading
• Supports both of Vue 1.0 and Vue 2.0

Table of Contents

• Demo
• Requirements
• Installation
• Usage
• Constructor Options
• Implementation
  • Basic
  • Css state
• Methods
  • Event hook
  • LazyLoadHandler
  • Performance
• Authors && Contributors
• License

Demo

Demo

Requirements

• Vue.js 1.x or 2.x

Installation

npm

$ npm install vue-lazyload

CDN

CDN: https://unpkg.com/vue-lazyload/vue-lazyload.js

<script src="https://unpkg.com/vue-lazyload/vue-lazyload.js"></script>
<script>
  Vue.use(VueLazyload)
  ...
</script>

Usage

main.js

import Vue from 'vue'
import App from './App.vue'
import VueLazyload from 'vue-lazyload'

Vue.use(VueLazyload)

// or with options
Vue.use(VueLazyload, {
  preLoad: 1.3,
  error: 'dist/error.png',
  loading: 'dist/loading.gif',
  attempt: 1
})

new Vue({
  el: 'body',
  components: {
    App
  }
})

Constructor Options

key	description	default	options
preLoad	proportion of pre-loading height	1.3	Number
error	src of the image upon load fail	'data-src'	String
loading	src of the image while loading	'data-src'	String
attempt	attempts count	3	Number
listenEvents	events that you want vue listen for	['scroll', 'wheel', 'mousewheel', 'resize', 'animationend', 'transitionend', 'touchmove']	Desired Listen Events
adapter	dynamically modify the attribute of element	{ }	Element Adapter
filter	the image's listener filter	{ }	Image listener filter
lazyComponent	lazyload component	false	Lazy Component
dispatchEvent	trigger the dom event	false	Boolean
throttleWait	throttle wait	200	Number
observer	use IntersectionObserver	false	Boolean
observerOptions	IntersectionObserver options	{ rootMargin: '0px', threshold: 0.1 }	IntersectionObserver

Desired Listen Events

You can configure which events you want vue-lazyload by passing in an array of listener names.

Vue.use(VueLazyload, {
  preLoad: 1.3,
  error: 'dist/error.png',
  loading: 'dist/loading.gif',
  attempt: 1,
  // the default is ['scroll', 'wheel', 'mousewheel', 'resize', 'animationend', 'transitionend']
  listenEvents: [ 'scroll' ]
})

This is useful if you are having trouble with this plugin resetting itself to loading when you have certain animations and transitions taking place

Image listener filter

dynamically modify the src of image

Vue.use(vueLazy, {
    filter: {
      progressive (listener, options) {
          const isCDN = /qiniudn.com/
          if (isCDN.test(listener.src)) {
              listener.el.setAttribute('lazy-progressive', 'true')
              listener.loading = listener.src + '?imageView2/1/w/10/h/10'
          }
      },
      webp (listener, options) {
          if (!options.supportWebp) return
          const isCDN = /qiniudn.com/
          if (isCDN.test(listener.src)) {
              listener.src += '?imageView2/2/format/webp'
          }
      }
    }
})

Element Adapter

Vue.use(vueLazy, {
    adapter: {
        loaded ({ bindType, el, naturalHeight, naturalWidth, $parent, src, loading, error, Init }) {
            // do something here
            // example for call LoadedHandler
            LoadedHandler(el)
        },
        loading (listender, Init) {
            console.log('loading')
        },
        error (listender, Init) {
            console.log('error')
        }
    }
})

IntersectionObserver

use Intersection Observer to to improve performance of a large number of nodes.

Vue.use(vueLazy, {
  // set observer to true
  observer: true,

  // optional
  observerOptions: {
    rootMargin: '0px', 
    threshold: 0.1
  }
})

Lazy Component

Vue.use(VueLazyload, {
  lazyComponent: true
});

<lazy-component @show="handler">
  <img class="mini-cover" :src="img.src" width="100%" height="400">
</lazy-component>

<script>
  {
    ...
    methods: {
      handler (component) {
        console.log('this component is showing')
      }
    }

  }
</script>

Implementation

Basic

vue-lazyload will set this img element's src with imgUrl string

<script>
export default {
  data () {
    return {
      imgObj: {
        src: 'http://xx.com/logo.png',
        error: 'http://xx.com/error.png',
        loading: 'http://xx.com/loading-spin.svg'
      },
      imgUrl: 'http://xx.com/logo.png' // String
    }
  }
}
</script>

<template>
  <div ref="container">
     <img v-lazy="imgUrl"/>
     <div v-lazy:background-image="imgUrl"></div>

     <!-- with customer error and loading -->
     <img v-lazy="imgObj"/>
     <div v-lazy:background-image="imgObj"></div>

     <!-- Customer scrollable element -->
     <img v-lazy.container ="imgUrl"/>
     <div v-lazy:background-image.container="img"></div>

    <!-- srcset -->
    <img v-lazy="'img.400px.jpg'" data-srcset="img.400px.jpg 400w, img.800px.jpg 800w, img.1200px.jpg 1200w">
    <img v-lazy="imgUrl" :data-srcset="imgUrl' + '?size=400 400w, ' + imgUrl + ' ?size=800 800w, ' + imgUrl +'/1200.jpg 1200w'" />
  </div>
</template>

CSS state

There are three states while img loading

loading loaded error

<img src="imgUrl" lazy="loading">
<img src="imgUrl" lazy="loaded">
<img src="imgUrl" lazy="error">

<style>
  img[lazy=loading] {
    /*your style here*/
  }
  img[lazy=error] {
    /*your style here*/
  }
  img[lazy=loaded] {
    /*your style here*/
  }
  /*
  or background-image
  */
  .yourclass[lazy=loading] {
    /*your style here*/
  }
  .yourclass[lazy=error] {
    /*your style here*/
  }
  .yourclass[lazy=loaded] {
    /*your style here*/
  }
</style>

Methods

Event Hook

vm.$Lazyload.$on(event, callback) vm.$Lazyload.$off(event, callback) vm.$Lazyload.$once(event, callback)

• $on Listen for a custom events loading, loaded, error
• $once Listen for a custom event, but only once. The listener will be removed once it triggers for the first time.
• $off Remove event listener(s).

vm.$Lazyload.$on

Arguments:

• {string} event
• {Function} callback

Example

vm.$Lazyload.$on('loaded', function ({ bindType, el, naturalHeight, naturalWidth, $parent, src, loading, error }, formCache) {
  console.log(el, src)
})

vm.$Lazyload.$once

Arguments:

• {string} event
• {Function} callback

Example

vm.$Lazyload.$once('loaded', function ({ el, src }) {
  console.log(el, src)
})

vm.$Lazyload.$off

If only the event is provided, remove all listeners for that event

Arguments:

• {string} event
• {Function} callback

Example

function handler ({ el, src }, formCache) {
  console.log(el, src)
}
vm.$Lazyload.$on('loaded', handler)
vm.$Lazyload.$off('loaded', handler)
vm.$Lazyload.$off('loaded')

LazyLoadHandler

vm.$Lazyload.lazyLoadHandler

Manually trigger lazy loading position calculation

Example

this.$Lazyload.lazyLoadHandler()

Performance

this.$Lazyload.$on('loaded', function (listener) {
  console.table(this.$Lazyload.performance())
})

Authors && Contributors

• hilongjw
• imcvampire
• darrynten
• biluochun
• whwnow
• Leopoldthecoder
• michalbcz
• blue0728
• JounQin
• llissery
• mega667
• RobinCK
• GallenHu

License

The MIT License