<!DOCTYPE HTML> <html data-expando-prop="xyz"> <!-- https://bugzilla.mozilla.org/show_bug.cgi?id=874758 --> <head> <meta charset="utf-8"> <title>Test for Bug 874758</title> <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script> <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/> <script type="application/javascript"> /** Test for Bug 874758 **/ Object.prototype.expandoProp = 5; is({}.expandoProp, 5, "Should see this on random objects"); is(document.head.dataset.expandoProp, 5, "Should see this on dataset too"); is(document.documentElement.dataset.expandoProp, "xyz", "But if the dataset has it, we should get it from there"); </script> </head> <body> <a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=874758">Mozilla Bug 874758</a> <p id="display"></p> <div id="content" style="display: none"> </div> <pre id="test"> </pre> </body> </html>