/bl-lazyload

Primary LanguageJavaScriptMIT LicenseMIT

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

Demo

Requirements

Installation

# npm
$ npm install vue-lazyload

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 src filter { } Image url filter

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 url filter

dynamically modify the src of image

Vue.use(vueLazy, {
    filter: {
      webp ({ src }) {
          const isCDN = /qiniudn.com/
          if (isCDN.test(src)) {
              src += '?imageView2/2/format/webp'
          }
          return src
      },
      someProcess ({ el, src }) {
        if (el.getAttribute('large')) {
          src += '?large'
        }
        return src
      }
    }
})

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')
        }
    }
})

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'" srcset="img.400px.jpg 400w, img.800px.jpg 800w, img.1200px.jpg 1200w">
    <img v-lazy="imgUrl" :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 }) {
  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 }) {
  console.log(el, src)
} 
vm.$Lazyload.$on('loaded', handler)
vm.$Lazyload.$off('loaded', handler)
vm.$Lazyload.$off('loaded')

Performance

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

performance-demo

Authors && Contributors

License

The MIT License