Issue 3515 - Added polyfill for the fetch() API

lib/polyfill/fetch.js

Index: lib/polyfill/fetch.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/polyfill/fetch.js
@@ -0,0 +1,61 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2015 Eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+(function(global)
+{
+  if ("fetch" in global)
+    return;
+
+  function Response(xhr)
+  {
+    this._xhr = xhr;
+  }
+  Response.prototype = {
+    get ok()
+    {
+      return this._xhr.status >= 200 && this._xhr.status <= 299;
+    },
+    text: function()
+    {
+      return Promise.resolve(this._xhr.responseText);
+    }
+  };
+
+  global.fetch = function(url)
+  {
+    return new Promise(function(resolve, reject)
+    {
+      var xhr = new XMLHttpRequest();
+
+      xhr.onload = function()
+      {
+        resolve(new Response(xhr));
+      };
+
+      xhr.onerror = xhr.onabort = function()
+      {
+        reject(new TypeError("Failed to fetch"));
+      };
+
+      xhr.overrideMimeType("text/plain");

[kzar, 2016/01/19 15:03:24]

I'm curious, why do this?

[Sebastian Noack, 2016/01/19 15:08:29]

Otherwise, XMLHttpRequest would try to parse the response if it is XML, HTML of
JSON. However, fetch() doesn't do any automatic parsing. So the parsed result is
ignored anyway, and if necessary the document would be parsed twice.

[kzar, 2016/01/19 15:41:02]

Acknowledged.

+      xhr.open("GET", url);
+      xhr.send();
+    });
+  };
+})(this);