The Tor Browser / file revision

 /* 

  * Any copyright is dedicated to the Public Domain.

  * http://creativecommons.org/licenses/publicdomain/

  * Contributor: haytjes <hv1989@gmail.com>

  */

 /* Check the undefined pattern is equivalent to empty string. */

 assertEq(RegExp(undefined).source, '');

 assertEq(RegExp(undefined).global, false);

 assertEq("test".replace(RegExp(undefined), "*"), '*test');

 assertEq(new RegExp(undefined).source, '');

 assertEq(new RegExp(undefined).global, false);

 assertEq('test'.replace(new RegExp(undefined), "*"), '*test');

 /* Global flags. */

 assertEq(new RegExp(undefined, "g").global, true);

 assertEq("test".replace(new RegExp(undefined, "g"), "*"), "*t*e*s*t*");

 assertEq(RegExp(undefined, "g").global, true);

 assertEq("test".replace(RegExp(undefined, "g"), "*"), "*t*e*s*t*");

 /* Undefined flags. */

 var re = new RegExp(undefined, undefined);

 assertEq(re.multiline, false);

 assertEq(re.global, false);

 assertEq(re.ignoreCase, false);

 var re = new RegExp("test", undefined);

 assertEq(re.multiline, false);

 assertEq(re.global, false);

 assertEq(re.ignoreCase, false);

 /* Flags argument that requires toString. */

 function Flags() {};

 Flags.prototype.toString = function dogToString() { return ""; }

 var re = new RegExp(undefined, new Flags());

 assertEq(re.multiline, false);

 assertEq(re.global, false);

 assertEq(re.ignoreCase, false);

 Flags.prototype.toString = function dogToString() { return "gim"; }

 var re = new RegExp(undefined, new Flags());

 assertEq(re.multiline, true);

 assertEq(re.global, true);

 assertEq(re.ignoreCase, true);