backbone_sync.js

Backbone.sync = function(method, model, options) {
  var type = methodMap[method];

  // Default options, unless specified.
  options || (options = {});

  // Default JSON-request options.
  var params = {type: type, dataType: 'json'};

  // Ensure that we have a URL.
  if (!options.url) {
    params.url = getValue(model, 'url') || urlError();
  }

  // Ensure that we have the appropriate request data.
  if (!options.data && model && (method == 'create' || method == 'update')) {
    params.data = model.toJSON();
  }

  if (type === 'PUT' || type === 'DELETE') {
    params.type = 'POST';
    params.beforeSend = function(xhr) {
      xhr.setRequestHeader('X-HTTP-Method-Override', type);
    };
  }

  // Make the request, allowing the user to override any Ajax options.
  return $.ajax(_.extend(params, options));
};