Backbone.sync implementation that use iframe + multipart/form-data

backbone.iframe.sync.js

(function () {
  Backbone.syncWithoutUpload = Backbone.sync
  Backbone.syncWithUpload = function(method, model, options) {
    // Create iframe
    var iframe_id = 'file_upload_iframe_' + Date.now()
      , iframe = jQuery('<iframe id="' + iframe_id + '" name="' + iframe_id + '" ></iframe>').hide()

    // Create an hidden form
    var authToken = jQuery('meta[name=csrf-token]').attr('content')
      , authParam = jQuery('meta[name=csrf-param]').attr('content')
      , push_session_id = Teambox.controllers.application.push_session_id

    var toForm = function(object, nested) {
      inputs = _.map(object, 
        function(attr, key) {
          if (nested) {
            var key = nested + '[' + key +']'
          }

          if ( _.isElement(attr) ) {
            return attr;
          } 

          var isNotEmpty = !_.isEmpty( attr )
            , isArray = _.isArray( attr )
            , isObject = ( typeof attr == 'object' )

          if ( isNotEmpty && (isArray || isObject) ) {
            return toForm( attr, key );
          }
  
          return jQuery('<input type="hidden" name"'+ key +'" value="'+ attr +'" />')[0];
        });

      return _.flatten(inputs);
    }

    var changeFormat = function(action) {
      if (action.endsWith('.text')) {
        return action.gsub(/\.text$/, '');
      }
      else {
        return action.gsub(/(\/?)$/, function (m) {
          return '.text';
        });
      }
    }

    var form = jQuery( '<form id="new_upload" enctype="multipart/form-data" target="'+ iframe_id +'" action="'+ changeFormat(model.url()) +'" method="POST">' +
                       '<input type="hidden" name="'+ authParam +'" value="'+ authToken +'" />' +
                       '<input type="hidden" name="_x-pushsession-id" class="x-pushsession-id" value="'+ push_session_id +'" />' +
                       '<input type="hidden" name="iframe" value="1" />' +
                       '</form>' ).hide();

    // Add attribute as input field
    _.each( toForm(model), function(el) {
      form.prepend(el)
    });

    jQuery(document.body).prepend(iframe);
    jQuery(document.body).prepend(form);

    function callback() {
      // contentDocument doesn't work in IE (7)
      var iframe_body = (iframe[0].contentDocument || iframe[0].contentWindow.document).body
        , response = JSON.parse(iframe_body.innerHTML);

      // TODO: Migrate to api v2. Make this check redundant
      response = response.objects ? response.objects : response;

      if (iframe_body.className !== "error") {
        var success = options.success
        if (success) options.success(response)
      } else {
        var error = options.error
        if (error) options.error(response)
      }

      iframe.remove();
      form.remove();
    }

    // Setup the iframe callback
    // for IE (7)
    iframe[0].onreadystatechange = function() {
      if (this.readyState === 'complete') {
        callback()
      }
    };

    // non-IE
    iframe[0].onload = callback;

    form[0].submit();
  }

  Backbone.sync = function(method, model, options) {
    if ( options && options.iframe ){
      Backbone.syncWithUpload(method, model, options)
    } else {
      Backbone.syncWithoutUpload(method, model, options)
    }
  };

}());