JavaScript has bad functional/monadic syntax.

Salesforce.js

{
  _ajax: function(path, method, data, retry) {
    var self = this;

    var response = self._session.pipe(function(session) {
      return $.ajax({
        type: method || "GET",
        url: SalesForceSettings.proxyUrl,
        cache: false,
        processData: false,
        data: data,
        contentType: "application/json",
        dataType: "json",
        headers: {
          "SalesforceProxy-Endpoint": session.serverUrl + "/services/data" + path,
          "X-Authorization": "OAuth " + session.sessionId,
          "X-User-Agent": "salesforce-toolkit-rest-javascript/" + SalesForceSettings.apiVersion
        }
      });
    });
    // Only return the first argument.
    if (retry) return response.pipe(function(json) { return json; });

    return response.pipe(
        function(json) { return json; },
        function(jqXHR) {
          if (jqXHR.status === 401) {
            return self._session.pipe(function(session) {
              return self._login(session.user.username,
                                 session.user.password,
                                 session.user.securityToken)
              .pipe(function() { return self._ajax(path, method, data, true); });
            });
          } else {
            return $.parseJSON(jqXHR.responseText)[0];
          }
        }).promise();
  }
}