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Image updater for responsive designs
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molt 2.1.0

The idea to develop molt comes from a few observations:

  • in responsive development we need to provide scaled scripts and images to not overload bandwidth and devices
  • web developers often provide images for all medias with only on-the-fly resizing, that is not optimized at all and not nice on all browsers
  • apply a display:none property to an img is not sufficient, the browser still download the file
  • Responsive-Images and responsive-images-alt don't support several image dimensions and the first one is a bit intrusive
  • responsiveImages is interesting but can't handle dynamic content generation on server side (with template engines)
  • it also could happen that we don't need images at all for 320px devices (per example)

Molt try to solve all these problems.

Also, it's W dependent and so can handle responsive events (it should be a good idea to read the W README file to well understand how it interacts with molt). So, if you've planned to use W in your website take the molt-xxx.min.js version, otherwise please take the molt-W-xxx.min.js one.


A molt image is set as a regular img tag on your HTML body (for dynamic generation purposes on server side), but with an url attribute:

<img url="images/img{320,1024}.jpg" display="block" alt="">

Numbers in brackets are modes. The selected mode will replace brackets: if the selected mode is 320 then the URL will look like images/img320.jpg. A mode is chosen like this:

  • if the current window/device width is, let's say, 240px then molt will choose the 320 mode
  • for a 480px width, the 320 mode again
  • but if a 1280px resolution is detected, the 1024 mode is chosen

You can also map modes into different values, for example using images/img-{320=small,1024=huge}.jpg to load either img-small.jpg or img-huge.jpg.

Moreover, note that you can 'negate' a mode, like !320, to make your images hidden for that mode (please take a look at the listener example to know how deal with that special mode).

Finally, the display attribute is used when a previously hidden image (by a negative mode) shows up again. Currently, there's no way to distinguish which display CSS property is set on a node (really, no way at all, coming from a lack of specs). So, molt will reset that display property to the display attribute value, inline otherwise.

You can apply several properties or launch some actions on a specific refreshed node (when a zoom event has been catched, per example) by listening its refreshing state:

// Get your image node
var img=$('#foo img')[0];
// Add a listener

Nodes are passed to the callback with the this keyword and current mode is directly accessible too. But, note that callbacks are only launched on non-negative modes.

To finish, molt must discover all your molt images to automatically manage them all:;

Oh yeah... If you want to handle non-javascript users to make them displaying images even so: forget it. There's, currently, no clean solution for that.

Ender integration

Some good news: molt is compatible with ender :)

var images=$('img');
        // blah!


Molt is released under the MIT license.

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