Current proposal, subject to change

Feature name Current browser Traceur EJS IE 11 FF 31 FF 32 CH 30[1] CH 33[1] CH 34[1] CH 35[1] CH 37[1] SF 7 WK KQ 4.13 RH PH Node Node harmony[2]
§Exponentiation operator Yes No No No No No No No No No No No No No No No No
§Array comprehensions Yes No No Yes Yes No No No No No No No No No No No No
§Generator comprehensions Yes No No Yes Yes No No No No No No No No No No No No
§Typed objects No No No No No No No No No No No No No No No No No
§Object.observe No No No No No No Yes Yes Yes Yes No No No No No No Yes
§Object.getOwnPropertyDescriptors No No No No No No No No No No No No No No No No No
§Reflect.Realm No No No No No No No No No No No No No No No No No

[1] Have to be enabled via "Experimental Javascript features" flag

[2] Have to be enabled via --harmony flag