Emerson Trait for lazy loading the correct images based on media query. Follows the same image list pattern as Foundation's Interchange

adaptive_image.js

/**
 * Combines some functionality of Foundation.interchange & custom Lazy Loading
 *
 * dependencies:
 * Foundation
 * jquery.viewport
 *
 * references:
 * http://foundation.zurb.com/docs/components/interchange.html
 * http://foundation.zurb.com/docs/javascript-utilities.html#media-queries
 */

(function($, define) {
  var trait = define('adaptive-image', {
    initialize : function initialize() {
      if(this.is(":in-viewport")){
        this.fetch();
      }
    },

    subscribe : {
      window : {
        'scroll' : function(ev) {
          if(this.is(":in-viewport") && this.attr('src').length <= 0){
            this.fetch();
          }
        }
      }
    }
  });
  trait.extend({
    fetch: function(){
      var image_srcs = this.data('image-srcs');
      _self = this;
      $.each(Foundation.libs.interchange.settings.named_queries, function(k,v){
        if(matchMedia(Foundation.libs.interchange.settings.named_queries[k]).matches){
          _self.imageFor(k,image_srcs);
        }
      });
    },
    imageFor: function(mediaQuery, imageList){
      imageArr = imageList.split(/\],\s?\[/);
      _self = this;
      $.each(imageArr, function(i,v){
        imgMqArr = v.replace(/(^\[|\]$)/g,'').split(',');
        rx = new RegExp("(" + mediaQuery + ")");
        if(imgMqArr[1].match(rx)){
          _self.attr('src', imgMqArr[0]);
        }
      });
    }
  });
})(Emerson.base, Emerson.trait);

application.js

// VENDOR
//= require vendor/jquery.viewport
//= require underscore
//= require emerson
//= require foundation

// TRAITS
//= require shared/traits/adaptive_image

$(function(){ $(document).foundation();});

(function($, window) {
  $(window).load(function() {
    Emerson.init();
  });
})($, this);

example.html.haml

=image_tag("", data: {traits: 'adaptive-image', image_srcs:"[//bevel-assets.s3.amazonaws.com/mobile/about-razor-box.jpg, (default)], [//bevel-assets.s3.amazonaws.com/mobile/about-razor-box@2x.jpg, (retina)]"})