IE9 Compatible XHR Adapter

ie9compatiblexhradapter.js

/**
 * Connection class to use with the elasticsearch.js client for limited compatibility with
 * IE 9 (also IE 8 is you include an es5 shim like https://github.com/es-shims/es5-shim).
 *
 * All connections from the browser, directly to elasticsearch, are assumed to be cross-domain
 * and therefore suffer from a lack of support in legacy browsers. To prevent the client from
 * behaving differently based on the browser version, the following limitations have been imposed
 * on all requests:
 *
 *  - only GET and POST are supported
 *  - Authentication can't be used
 *  - Custom headers can't be set
 *  - Requests can't be made to localhost unless the page is running on localhost
 *  - Protocols of the parent window and the request must match.
 *
 * Also because of restrictions put in place by IE8/9, responses will be different
 * in the following ways:
 *  - Status codes are not available for the responses
 *  - Any non-20x status code is considered a generic error. No response body will be available
 *
 * @class  Ie9CompatibleXhrConnector
 */
window.Ie9CompatibleXhrConnector = (function () {

  var EsXhrConnection = elasticsearch.ConnectionPool.connectionClasses.xhr;
  var ConnectionFault = elasticsearch.errors.ConnectionFault;

  // perminent references
  var ModernXhr = window.XMLHttpRequest;
  var LegacyXhr = window.XDomainRequest;
  var setImmediate = window.setImmediate || function (cb) { setTimeout(cb, 1); };

  var currentProtocol = window.location.protocol.substr(0, window.location.protocol.length - 1);
  var localhostRE = /:\/\/(localhost|127\.0\.0\.1)[:\/]/;

  function Ie9CompatibleXhrConnector(host, config) {
    EsXhrConnection.call(this, host, config);

    this._XhrConstructor = (function () {
      if (typeof ModernXhr !== 'undefined') {
        var req = new ModernXhr();
        if ('withCredentials' in req) {
          return ModernXhr;
        }
      }

      if (typeof LegacyXhr !== 'undefined') {
        return LegacyXhr;
      }

      throw new Error('Unable to find a suitable Cross-Domain AJAX handler.');
    }());
  }
  // inherit EsXhrConnection's prototype
  Ie9CompatibleXhrConnector.prototype = Object.create(EsXhrConnection.prototype, { 'constructor': Ie9CompatibleXhrConnector });

  Ie9CompatibleXhrConnector.prototype.request = function (params, cb) {
    var xhr = new this._XhrConstructor();

    // This is a patch to this.host by Tim Raymond to get results working
    // on search. It isn't really necessary for that page.
    this.host.getHeaders = function() { return false };

    var hasHeaders = !!this.host.getHeaders(params.headers);
    var url = this.host.makeUrl(params);
    var log = this.log;
    var hasAuth = this.host.auth;
    var method = (params.method || 'GET').toUpperCase();

    var err = function (msg) {
      // always callback async
      setImmediate(function () {
        cb(new TypeError('Cross-domain AJAX requests ' + msg + ' are not supported'));
      });
    };

    /**
     * To prevent some browsers from behaving differently from others, implement some checks here
     */

    if (method !== 'GET' && method !== 'POST') {
      return err('using HTTP method ' + method);
    }

    if (localhostRE.test(url) && !localhostRE.test(window.location.href)) {
      return err('to localhost from other domains');
    }

    if (hasAuth) {
      return err('with authentication');
    }

    if (hasHeaders) {
      return err('with custom headers');
    }

    if (this.host.protocol !== currentProtocol) {
      return err('across protocols');
    }

    /**
     * Setup listeners for the response
     */
    if (this._XhrConstructor === LegacyXhr) {
      // XDomainRequest does not support onreadystatechange
      xhr.onload = function () {
        log.trace(params.method, url, params.body, xhr.responseText, xhr.status);
        cb(void 0, xhr.responseText, 200);
      };

      // XDomainRequest also sends errors elsewhere
      xhr.onerror = function (err) {
        log.trace(params.method, url, params.body, xhr.responseText, xhr.status);
        cb(new ConnectionFault(err.message), xhr.responseText, void 0);
      };
    }

    if (this._XhrConstructor === ModernXhr) {
      xhr.onreadystatechange = function () {
        if (xhr.readyState === 4) {
          log.trace(params.method, url, params.body, xhr.responseText, xhr.status);
          var err = xhr.status ? void 0 : new ConnectionFault(xhr.statusText || 'Request failed to complete.');
          cb(err, xhr.responseText, xhr.status);
        }
      };
    }

    /**
     * Send the request
     */
    xhr.open(method, url);
    xhr.send(params.body || void 0);

    return function () {
      xhr.abort();
    };
  };

  return Ie9CompatibleXhrConnector;
}());