Use XMLHttpRequest instead of jQuery.

Author: RubenVerborgh

lib/browser/.eslintrc

@@ -1,6 +1,6 @@
 {
   globals: {
-    jQuery: true,
+    XMLHttpRequest: true,
   },
 }
 

lib/browser/Request.js

@@ -1,5 +1,5 @@
 /*! @license MIT ©2013-2016 Ruben Verborgh - Ghent University / iMinds */
-/* Single-function HTTP(S) request module for browsers using jQuery */
+/* Single-function HTTP(S) request module for browsers */
 
 var EventEmitter = require('events').EventEmitter,
     AsyncIterator = require('asynciterator'),
@@ -9,57 +9,72 @@ var EventEmitter = require('events').EventEmitter,
 require('setimmediate');
 
 // Headers we cannot send (see https://www.w3.org/TR/XMLHttpRequest/#the-setrequestheader()-method)
-var UNSAFE_REQUEST_HEADERS = ['accept-encoding', 'user-agent', 'referer'];
-// Headers we need to obtain
-var RESPONSE_HEADERS = ['content-type', 'content-location', 'link', 'memento-datetime'];
+var UNSAFE_REQUEST_HEADERS = _.object(['accept-encoding', 'user-agent', 'referer']);
 
 // Resources that were already time-negotiated
 var negotiatedResources = Object.create(null);
 
 // Creates an HTTP request with the given settings
 function createRequest(settings) {
-  var request = new EventEmitter();
-
   // PERFORMANCE HACK:
   // Reduce OPTIONS preflight requests by removing the Accept-Datetime header
   // on requests for resources that are presumed to have been time-negotiated
   if (negotiatedResources[removeQuery(settings.url)])
     delete settings.headers['accept-datetime'];
 
-  // Delegate the request to jQuery's AJAX module
-  var jqXHR = jQuery.ajax({
-    url: settings.url,
-    timeout: settings.timeout,
-    type: settings.method,
-    headers: _.omit(settings.headers, UNSAFE_REQUEST_HEADERS),
-  });
-  // Emit the result as a readable response iterator
-  jqXHR.then(function () {
-    var response = AsyncIterator.single(jqXHR.responseText || '');
-    response.statusCode = jqXHR.status;
-    response.headers = _.object(RESPONSE_HEADERS, RESPONSE_HEADERS.map(jqXHR.getResponseHeader));
-    request.emit('response', response);
+  // Create the actual XMLHttpRequest
+  var request = new XMLHttpRequest(), reqHeaders = settings.headers;
+  request.open(settings.method, settings.url, true);
+  request.timeout = settings.timeout;
+  for (var header in reqHeaders) {
+    if (!(header in UNSAFE_REQUEST_HEADERS) && reqHeaders[header])
+      request.setRequestHeader(header, reqHeaders[header]);
+  }
+
+  // Create a proxy for the XMLHttpRequest
+  var requestProxy = new EventEmitter();
+  requestProxy.abort = function () { request.abort(); };
+
+  // Handle the arrival of a response
+  request.onload = function () {
+    // Convert the response into an iterator
+    var response = AsyncIterator.single(request.responseText || '');
+    response.statusCode = request.status;
+
+    // Parse the response headers
+    var resHeaders = response.headers = {},
+        rawHeaders = request.getAllResponseHeaders() || '',
+        headerMatcher = /^([^:\n\r]+):[ \t]*([^\r\n]*)$/mg, match;
+    while (match = headerMatcher.exec(rawHeaders))
+      resHeaders[match[1].toLowerCase()] = match[2];
+
+    // Emit the response
+    requestProxy.emit('response', response);
 
-    // If the resource was time-negotiated, store its "base" URI (= no query string)
-    if (settings.headers['accept-datetime'] && response.headers['memento-datetime']) {
-      var resource = removeQuery(response.headers['content-location'] || settings.url);
+    // If the resource was time-negotiated, store its queryless URI
+    // to enable the PERFORMANCE HACK explained above
+    if (reqHeaders['accept-datetime'] && resHeaders['memento-datetime']) {
+      var resource = removeQuery(resHeaders['content-location'] || settings.url);
       if (!negotiatedResources[resource]) {
         // Ensure the resource is not a timegate
-        var links = response.headers.link && parseLink(response.headers.link),
+        var links = resHeaders.link && parseLink(resHeaders.link),
             timegate = removeQuery(links && links.timegate && links.timegate.url);
         if (resource !== timegate)
           negotiatedResources[resource] = true;
       }
     }
-  },
-  // Emit an error if the request fails
-  function () {
-    request.emit('error', new Error('Error requesting ' + settings.url));
-  });
-  // Aborts the request
-  request.abort = function () { jqXHR.abort(); };
+  };
+  // Report errors and timeouts
+  request.onerror = function () {
+    requestProxy.emit('error', new Error('Error requesting ' + settings.url));
+  };
+  request.ontimeout = function () {
+    requestProxy.emit('error', new Error('Timeout requesting ' + settings.url));
+  };
 
-  return request;
+  // Execute the request
+  request.send();
+  return requestProxy;
 }
 
 // Removes the query string from a URL