External image loader for chrome apps

imgLoader.coffee

# Just pass in the parent of the image tags.
# Image tags should have a .external-img class and data-src should be the external url

define ->
  cache = {}

  loader = ($el) ->
    lazyLoad = (img) ->
      el = $ img
      url = el.attr 'data-src'
      return el.attr('src', cache[url]) if cache[url]?
      xhr = new XMLHttpRequest
      xhr.open 'GET', url
      xhr.responseType = 'blob'
      xhr.onload = (e) ->
        blob = window.webkitURL.createObjectURL @response
        cache[url] = blob
        el.attr 'src', blob
      xhr.send()

    imgs = $el.find(".external-img")
    lazyLoad img for img in imgs
    return $el

  return loader