@area17/a17-lazyload

A17 Lazy Load

• Demos http://lazyload.dev.area17.com/
• Issues https://code.area17.com/a17/a17-lazyload/issues

Introduction

A straight forward lazy loader using IntersectionObserver if available and if not, it uses a requestAnimationFrame loop if available. If neither are available it does nothing.

When a watched element is in the view port it swaps data-src/data-srcset on img, source and iframe to src/srcset. It also adds a load listener and removes the data- attribute on load to allow you to hook styles up to the two different states.

If data-srcset to srcset and typeof picturefill, attempts to run picturefill() on the element.

When it runs out of elements to watch, the loop ends.

More detailed instructions on usage are at: http://lazyload.dev.area17.com/

Usage

<script src="path/to/a17-lazyload.min.js"></script>
<script>
  lazyload();
</script>

Also available via NPM:

npm install @area17/a17-lazyload

import lazyload from '@area17/a17-lazyload';

lazyload();

Issues/Contributing/Discussion

If you find a bug in a17-lazyload, please add it to the issue tracker or fork it, fix it and submit a pull request for it (👍).

The development script is dist/a17-lazyload.js. Tabs are 2 spaces, functions are commented, variables are camel case and its preferred that its easier to read than outright file size being the smallest possible.

Make sure to include a minified version inside of dist by running: npm run minify (you'll need to npm run install to install terser). The minified version is added to the git repository for users who aren't using build tools.

Support

IE10+ because of the use of requestAnimationFrame if no IntersectionObserver.

Coming soon

• Work in check for loading="lazy" support: https://addyosmani.com/blog/lazy-loading/
• Use a MutationObserver to check for dynamically added elements to check.

Filesize

• ~7kb uncompressed
• ~3kb minified
• ~1kb minified and gzipped