Haml use jQuery 1.x for old IE, 2.x for all other browsers

jquery.haml

- jquery_1x = 'jquery-1.11.0-beta2.min.js'
- jquery_2x = 'jquery-2.1.0-beta2.min.js'

/[if lt IE 9]
  -# The user is on an ancient browser.  Load jQuery 1.x from the CDN.
  %script{src: "http://code.jquery.com/#{jquery_1x}"}

  -# If loading jQuery from the CDN fails, then load our local copy.
  :javascript
    window.jQuery || document.write(
      '<script src="#{uri('/javascripts/vendor/' << jquery_1x)}">' +
      '<\/script>'
    );

= surround '<!--[if gte IE 9]><!-->', '<!--[endif]-->' do
  -# The user is on a modern browser.  Load jQuery 2.x from the CDN.
  %script{src: "http://code.jquery.com/#{jquery_2x}"}

  -# If loading jQuery from the CDN fails, then load our local copy.
  :javascript
    window.jQuery || document.write(
      '<script src="#{uri('/javascripts/vendor/' << jquery_2x)}">' +
      '<\/script>'
    );