Please note that these tests represent existence, not functionality or full conformance. I hope to test conformance sometime in the future.

IE 7 IE 8 IE 9 IE 10 FF 3 FF 3.5, 3.6 FF 4-8 SF 3.2 SF 4 SF 5 SF 5.1 WebKit CH 5 CH 6 CH 7-12 CH 13-16 OP 10.1 OP 10.50-11.50 OP 12 Konq 4.3 BESEN Rhino 1.7
Object.create No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes No No Yes No Yes Yes
Object.defineProperty No Yes [1] Yes Yes No No Yes No No Yes [5] Yes Yes [5] Yes Yes Yes Yes No No Yes No Yes Yes
Object.defineProperties No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes No No Yes No Yes Yes
Object.getPrototypeOf No No Yes Yes No Yes Yes No No Yes Yes Yes Yes Yes Yes Yes No No Yes No Yes Yes
Object.keys No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes No No Yes No Yes Yes
Object.seal No No Yes Yes No No Yes No No No Yes Yes No Yes Yes Yes No No Yes No Yes Yes
Object.freeze No No Yes Yes No No Yes No No No Yes Yes No Yes Yes Yes No No Yes No Yes Yes
Object.preventExtensions No No Yes Yes No No Yes No No No Yes Yes No Yes Yes Yes No No Yes No Yes Yes
Object.isSealed No No Yes Yes No No Yes No No No Yes Yes No Yes Yes Yes No No Yes No Yes Yes
Object.isFrozen No No Yes Yes No No Yes No No No Yes Yes No Yes Yes Yes No No Yes No Yes Yes
Object.isExtensible No No Yes Yes No No Yes No No No Yes Yes No Yes Yes Yes No No Yes No Yes Yes
Object.getOwnPropertyDescriptor No Yes Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes No No Yes No Yes Yes
Object.getOwnPropertyNames No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes No No Yes No Yes Yes
Date.prototype.toISOString No No Yes Yes No Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes No Yes Yes
Date.now No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes
Array.isArray No No Yes Yes No No Yes No No Yes Yes Yes Yes Yes Yes Yes No Yes Yes No Yes Yes
JSON No Yes Yes Yes No Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes No Yes Yes
Function.prototype.bind No No Yes Yes No No Yes No No No No No No No Yes Yes No No Yes No Yes Yes
String.prototype.trim No No Yes Yes No Yes Yes No No Yes Yes Yes Yes Yes Yes Yes No Yes Yes No Yes Yes
Array.prototype.indexOf No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Array.prototype.lastIndexOf No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Array.prototype.every No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Array.prototype.some No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Array.prototype.forEach No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Array.prototype.map No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Array.prototype.filter No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Array.prototype.reduce No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes
Array.prototype.reduceRight No No Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes Yes Yes
Getter in property initializer No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Setter in property initializer No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Property access on strings [2] No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Reserved words as property names [3] No No Yes Yes Yes Yes Yes No No No Yes Yes No No Yes Yes No No Yes No Yes No
Strict mode [4] No No No No[6] No No Yes No No No Yes Yes No No No Yes No No Yes No Yes No

[1] In Internet Explorer 8 Object.defineProperty only accepts DOM objects (MSDN reference).

[2] For example: "foobar"[3] === "b"

[3] For example: ({ if: 1 })

[4] Strict mode is assumed to be supported when the following expression evaluates to true — (function(){ "use strict"; return !this; })();

[5] In some versions of WebKit Object.defineProperty does not work with DOM objects.

[6] IE10 PP2 has a bug with strict mode which makes the following expression "fail", even though strict mode is more or less supported: (function(){ "use strict"; return !this })()