The Tor Browser / file revision

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 if (typeof isHighSurrogate === 'undefined') {

     var isHighSurrogate = function isHighSurrogate(s) {

         var c = s.charCodeAt(0);

         return c >= 0xD800 && c <= 0xDBFF;

     }

 }

 if (typeof isLowSurrogate === 'undefined') {

     var isLowSurrogate = function isLowSurrogate(s) {

         var c = s.charCodeAt(0);

         return c >= 0xDC00 && c <= 0xDFFF;

     }

 }

 if (typeof isSurrogatePair === 'undefined') {

     var isSurrogatePair = function isSurrogatePair(s) {

         return s.length == 2 && isHighSurrogate(s[0]) && isLowSurrogate(s[1]);

     }

 }