Backbone.ajax with window.fetch

backbone.fetch.js

var defaults = function(obj, source) {
  for (var prop in source) {
    if (obj[prop] === undefined) obj[prop] = source[prop];
  }
  return obj;
}

var stringifyGETParams = function(url, data) {
  var query = '';
  for (var key in data) {
    if (data[key] == null) continue;
    query += '&'
      + encodeURIComponent(key) + '='
      + encodeURIComponent(data[key]);
  }
  if (query) url += (~url.indexOf('?') ? '&' : '?') + query.substring(1);
  return url;
}

var status = function(response) {
  if (response.status >= 200 && response.status < 300) {
    return response;
  }
  throw new Error(response.statusText);
}

var json = function(response) {
  return response.json()
}

Backbone.ajax = function(options) {
  if (options.type === 'GET' && typeof options.data === 'object') {
    options.url = stringifyGETParams(options.url, options.data);
  }

  return fetch(options.url, defaults(options, {
    method: options.type,
    headers: defaults(options.headers || {}, {
      'Accept': 'application/json',
      'Content-Type': 'application/json'
    }),
    body: options.data
  }))
  .then(status)
  .then(json)
  .then(options.success)
  .catch(options.error);
};

Do I understand correctly - with this plugin BB.ajax-returned promise is never rejected because the last line will not re-throw any error?

Right, you could just kill that line if you don't need options.error or rethrow/Promise.reject() yourself in the catch if you do. This is mostly for demo, you might want to add your own logic in your app.

Pretty simple change to keep the promises alive and kickin...

.then(function (result) {
  options.success.apply(this, arguments);
  return result;
})
.catch(function (err) {
  options.error.apply(this, arguments);
  throw err;
});