Historically, you couldn't use ANY of them as object literal keys without risking problems. I believe it was an oversight.

JS has reserved a really long list of keywords that have been around for a long time.. I've seen this occasionally trip up new JS programmers because the words are special without having any use.

abstract, arguments, await, boolean, break, byte, case, catch, char, class, const, continue, debugger, default, delete, do, double, else, enum, eval, export, extends, false, final, finally, float, for, function, goto, if , implements, import, in, instanceof, int, interface, let, long, native, new, null, package, private, protected, public, return, short, static, super, switch, synchronized, this, throw, throws, transient, true, try, typeof, var, void, volatile, while, with, yield