ab-interchange

AB-interchange

AB-interchange is a small, dependencie free and vanilla JavaScript component that conditionnaly load things depending on media queries and it also has a powerfull lazy-loading option:

• img
• picture
• background-image
• HTML content (Ajax)

It's damn small: about 2500 bytes (uglyfied and GZipped). It is used in the French website of ENGIE.

Have a look at the Codepen demonstration.

Install

Install with npm:

npm install --save ab-interchange

Install with yarn:

yarn add ab-interchange

Setup

You can then import it in your JS bundle (webpack, ES6, browserify...):

import abInterchange from 'ab-interchange';

Or loading the js right before </body> if you are not using a builder.

Because of the usage of matchMedia and requestAnimationFrame, compatibility start with IE 10. To rise compatibility up to IE 9, you can add matchMedia polyfill and requestAnimationFrame polyfill.

Usage

Follow AB-mediaQuery readme to configure it the way you like depending on your needs. For exemple:

abMediaQuery({
  bp: {
    smallOnly:  'screen and (max-width: 767px)',
    mediumOnly: 'screen and (min-width: 768px) and (max-width: 1024px)',
    medium:     'screen and (min-width: 768px)',
    largeOnly:  'screen and (min-width: 1025px) and (max-width: 1280px)',
    large:      'screen and (min-width: 1025px)'
  }
});

Then you only need to initialize with AB.interchange() or with some options:

abInterchange({
  mode:        'background',
  lazy:        false,
  lazySettings: {
    placeholder: false, // trick to prevent reflow of the page
    offscreen:   1.5,   // load items only when in the view + 0.5
    delayed:     false,
    layout:      'fluid' // can be "fixed" to fixed dimensions (not fluid)
  }
});

Then use data-ab-interchange attribute to pass options on each elemets if needed.

data-ab-interchange-src attribute is where you define different sources and breakpoints defined with AB-mediaQuery. It should contain a list of arrays with the path to the asset and the breakpoint name. Beware to respect mobile first order. Order is VERY important!

Examples

img

Recommanded usage to prevent reflow with lazy loading enabled:

<div
  alt=""
  width="100"
  height="75"
  data-ab-interchange='{"lazy": true, "lazySettings": {
    "placeholder": true,
    "offscreen":   1,
    "delayed":     2000
  }}"'
  data-ab-interchange-src="[xxx, smallOnly], [xxx, medium]">
</div>

If your images have different ratio depending on media query:

<div
  alt=""
  width='{"smallOnly": 20, "medium": 50}'
  height='{"smallOnly": 20, "medium": 50}'
  data-ab-interchange='{"lazy": true, "lazySettings": {
    "placeholder": true,
    "offscreen":   1,
    "delayed":     2000
  }}"'
  data-ab-interchange-src="[xxx, smallOnly], [xxx, medium]">
</div>

Or on normal img tags:

<img
  alt=""
  width="100"
  height="75"
  data-ab-interchange='{"lazy": true}"'
  data-ab-interchange-src="[xxx, smallOnly], [xxx, medium]"/>

picture

<picture>
  <source srcset="xxx" media="(min-width: 80em)"/>
  <source srcset="xxx" media="(min-width: 64em)"/>
  <source srcset="xxx" media="(min-width: 48em)"/>
  <source srcset="xxx"/>
  <img
    alt=""
    width="100"
    height="75"
    data-ab-interchange
    data-ab-interchange-src="[xxx, smallOnly], [xxx, medium]"/>
</picture>

background-image

<div
  data-ab-interchange='{"mode": "background", "lazy": true, "lazySettings": {"offscreen": 1.5}"}'
  data-ab-interchange-src="[xxx, smallOnly], [xxx, medium]">
</div>

XMLHttpRequest content (Ajax)

<div
  data-ab-interchange='{"mode": "ajax"}'
  data-ab-interchange-src="[xxx, smallOnly], [xxx, mediumOnly]">
</div>

JS event

replaced.ab-interchange event is automatically triggered when an IMG (or else) changed. For IMG and HTML, it's fired only when the new content is loaded, for background-image, immediatly, because it does not impact the layout:

window.addEventListener('replaced.ab-interchange', function(e){
  console.log(e.detail.element);
});