<!DOCTYPE html> <html> <!-- https://bugzilla.mozilla.org/show_bug.cgi?id=856384 --> <head> <meta charset="UTF-8"> <title>Test for Bug 856384</title> <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script> <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/> </head> <body> <a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=856384">Mozilla Bug 856384</a> <p id="display"></p> <div id="content" style="display: none"> </div> <iframe name="constructor" src="about:blank"></iframe> <pre id="test"> <script type="application/javascript"> SimpleTest.waitForExplicitFinish(); function run() { is(Object.isExtensible(window), true, "Windows are extensible by default"); try { Object.preventExtensions(window); throw "didn't throw"; } catch (e) { is(e instanceof TypeError, true, "preventExtensions(window) should throw a TypeError, instead got: " + e); is(Object.isExtensible(window), true, 'Windows are extensible after an extensibility "change" attempt'); } SimpleTest.finish(); } window.addEventListener("load", run, false); </script> </pre> </body> </html>