lazyloadjs

v3.2.2

Published

2 years ago

Image lazy loading

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lazyload

Lazyload images, iframes or any src* element until they are visible in the viewport.

Install

npm install lazyloadjs --save

Simple example

See more examples.

<!DOCTYPE html>
<html>
  <head>
    <title>lazyload</title>
  </head>
  <body>
    <script src="lazyload.min.js"></script>

    <!-- A lot of content -->
    <!-- A lot of content -->

    <img
      data-src="real/image/src.jpg"
      src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw=="
      onload="lzld(this)">
  </body>
</html>

Make sure your webpage is in standards mode.

Viewport computing is badly handled by browsers when in quirksmode.

If you do not want to use a data-uri as your src, you can also use the provided b.gif which is the tiniest gif ever.

On most websites, you better let the first top images not bound to lzld method. So that they shows really fast.

Advanced example

lazyloadjs is an npm module and is compatible with browserify.

global.myLazyload = require('lazyloadjs')();

<img
  data-src="real/image/src.jpg"
  src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw=="
  onload="myLazyload(this)">

Per default, lazyloadjs exposes the lzld instance on the global object. So that in most cases, you just need to require it in your webpage.

API

var lzld = lazyload([opts])

opts is an object with these defaults:

{
  container: document.body,
  offset: 333,
  src: 'data-src' // or function(elt) { return customSrc }
}

opts.container is the referencing container, it's the viewport, defaults to document.body

opts.offset is a length in pixels used to compute when an element will soon be visible. So that you load it just before it becomes visible.

src is the attribute name storing the real src of the element to load.

src can also be a function, so that you can have your custom src computing algorithm. You can use it to lazyload High DPI/retina images.

Launching the examples

npm run examples

Developing

Launch the dev server:

npm run dev

Browse to http://localhost:8080/__zuul.

Tests are written with mocha.

Building

We provide a pre-built version of lazyloadjs in build/lazyload.min.js.

But you can build your own:

npm run build

You get the build in build/lazyload.min.js.

Please consider using browserify.

Sites using lazyload

Tens of millions of pageviews are served each month using this project:

fasterize.com lazyload was first developed at fasterize (WPO solution)
lemonde.fr
pluzz.francetv.fr
pcinpact.com
elpais.com
playtv.fr
voyages-sncf.com
rue89.com
flipkart.com
clubic.com
achetezfacile.com
mapado.com
decitre.fr
base-orb.fr

.. And many unlisted websites, add yours!

Licence

Also see LICENCE.fasterize

(The MIT Licence)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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