blazy

#hey, be lazy

bLazy is a lightweight script for lazy loading and multi-serving images, iframes, videos and more (less than 1.4KB minified and gzipped). It’s written in pure JavaScript why it doesn’t depend on 3rd-party libraries such as jQuery. It lets you lazy load and multi-serve your images so you can save bandwidth and server requests. The user will have faster load times and save data usage if he/she doesn't browse the whole page.

Table of Contents

1. Demo

2. Usage & API

3. Why be lazy?

4. Changelog

5. License

DEMO ##

http://dinbror.dk/blazy/

More examples:
http://dinbror.dk/blazy/examples/

Codepen playground:
http://codepen.io/dinbror/pen/HzCAJ

USAGE & API ##

http://dinbror.dk/blog/blazy/

$3

You can install blazy.js with npm:
`` npm
npm install blazy --save
`
or bower:
` bower
bower install blazy --save
`

$3

If you don't want to host the script yourself you can link to the latest minified file:
//cdn.jsdelivr.net/blazy/latest/blazy.min.js on jsDelivr.
Exchange latest with the specific version number if you want to lock it in.

WHY BE LAZY? ##

* bLazy is used on big sites with millions of monthly visitors so it has been tested out in the real world.
* bLazy is written in pure JavaScript why it doesn’t depend on 3rd-party libraries such as jQuery.
* bLazy is lightweight, less than 1.4KB and less than 1.25KB if you don't need IE7- support.
* bLazy is very fast. It has focus on performance why it also auto-destroys when it's done lazy loading.
* bLazy can lazy load all types of images including background images.
* bLazy is future-proof. It supports srcset and the picture element.
* bLazy can serve retina images on retina devices.
* bLazy can lazy load everything with a src like iframes, HTML5 videos, scripts, unity games etc.
* bLazy supports all browsers used today including legacy browsers like IE7 and 8.
* bLazy supports all main module formats like AMD, CommonJS and globals.

WISHLIST/NEW FEATURES REQUESTED BY YOU

* Only preload "first frame" of progressive jpegs.
* Add support for CSS background property; image-set (caniuse).
* Add a class when the lazyloading begins.
* Option to keen load once on screen images have loaded.
* Add option to disable success/error classes
* Animate the container that contains the image you lazy load. You can do that today by adding/removing a class in the success callback.

CHANGELOG

$3

* Added null check in public load function.
* Bugfix: Fixed this issue defaulting to window when passing revalidate or destroy in setTimeout as reference #73 and #112. Thanks PeteDuncanson.
* Bugfix: If parts of container is outside window use the viewport boundaries #113 and #114. Thanks dbirkbeck.

$3

* Bugfix: Created polyfill and check for support of Element.closest which was introduced in the container fix in v. 1.8.0.

$3

* Bugfix: Non-visible images being loaded inside container #23 and #96.

$3

* Bugfix: In safari the picture element always loaded the default/fallback image #92.

$3

* Bugfix: When lazyloading picture elements it also loaded the fallback/regular image #92 and 108. Thanks @idoshamun
* Refactored loadElement function to avoid redundancy.

$3

* Bugfix: When lazyloading srcset images it also loaded the fallback/regular image #99. Thanks @m0uH

$3

* Changed event listener to passive listener #106. Thanks @idoshamun
* Added support for web components (shadow dom) #107. Thanks again @idoshamun

$3

* Fixed bug introduced in v.1.6.0, not using retina/breakpoint src #90.

$3

* Implemented a workaround for onload/onerror bug introduced in chrome v50, LINK. Fixed #85.

$3

* Added support for srcset and the picture element. Fixed #69, #75, #77 and #82.
* Added support for lazy load of videos with sources. Fixed #81.
* Bugfix. Ensuring that error and success classes won't be added multiple times. Fixed #84.
* Marked breakpoints as obsolete. Will be removed in upcoming version. Use srcset and/or the picture element instead.

$3

* Fixed two Safari bugs: #66 and #78. Ensuring "DOM ready".

$3

* Implemented #30. Keeping data source until success.
* Fixed #47. After implementing #30 you can now get the image src and more information in the error/success callbacks.
* Added example page to repo /example/index.html.

$3

* Fixed minor bug where the error class was added when calling revalidate().
* Minor refactoring

$3

* Fixed toArray function so it now works in IE7 + 8 again. Bug introduced in 1.4.0. Thanks for reporting @imcotton.
* Fixed #41. Added options for validate and saveViewportOffset delay.

$3

* Added new feature. Now you can lazy load everything with a src attribute like iframes, unity games etc.
* Fixed #45. Now you can pass an option if you always want to load invisible images/elements.
* Fixed #49. Expanded the load function so it's now possible to pass a list of elements instead of only one element. Tested with getElementById, getElementsByClassName, querySelectorAll, querySelector and jQuery selector.
* Fixed #63.

$3

* Fixed #60. An "Uncaught TypeError" when options is null introduced in the refactoring in version 1.4.0.

$3

* Fixed #56. Now it's possible to create multiple versions of blazy without overriding options.

$3

* Added support for CommonJS-like environments that support module.exports like node.

$3

* Fixed #34. Expanded public load function with force attribute, so you can force hidden images to be loaded.
* Fixed #24, #32 and #35. Updated "elementInView" function with intersection check. Thanks @teohhanhui.

$3

* Fixed #15, when you resize the browser window in another tab bLazy didn't trigger new images in view. Thanks joshribakoff.

$3

* When lazy loading background images it now only updates the background-image css attribute. Thanks Saku.

$3

* Important note: renamed option multi to breakpoints because it's much more descriptive.
* Added AMD support.
* Minor refactoring.

$3

* Fixed hardcoded retina check (isRetina = true).
* Fixed "Uncaught TypeError" when data-src is null. Instead it'll trigger the error callback.

$3

* New feature: After many requests I added the possibility to handle retina images (if you’re not doing retina-first).
* New feature: Now you can also lazy load background images.
* Added new option, separator. Used if you want to pass retina images, default separator is ‘|’. (data-src=“image.jpg|image@2x.jpg”).

$3

* Fixed #1, resize/scroll events may be detached when adding elements by ajax.
* Added new option, errorClass. Classname an image will get if something goes wrong, default is ‘b-error’.
* Renamed option loadedClass to successClass so naming is aligned. Default is still ‘b-loaded’.

$3

* Renamed success callback from onLoaded to success.
* Added onerror callback; error.
* Added the possibility to pass multiple containers instead of one.

$3

* Fixed "Uncaught TypeError" when container isn't default (window).

$3

* Added null check so we won't try to load an image if it's missing a data source.

$3

* Added new option, loadedClass`. Classname an image will get when loaded.
* Added support for horizontal lazy loading.
* Reduced throttle time for validate.

$3

* Fixed typo in unbindEvent function.
* Added support for IE7 as promised (fallback for querySelectorAll).

$3

* Performance improvements.
* Added throttle function to ensure that we don't call resize/scroll functions too often.
* Cleaning image markup when image has loaded.

##LICENSE:
Copyright (c) 2013-16 Bjørn Klinggaard. Licensed under the The MIT License (MIT).