Number.prototype not being an instance breaks the web, too

Andreas Rossberg rossberg at
Mon Apr 13 14:47:22 UTC 2015

V8 just rolled a change into Canary yesterday that implements the new ES6
semantics for Number.prototype (and Boolean.prototype) being ordinary
objects. Unfortunately, that seems to break the web. In particular fails to load now.

What I see happening on that page is a TypeError "Number.prototype.valueOf
is not generic" being thrown in this function (probably part of moo tools):

Number.prototype.$family = function(){
return isFinite(this) ? 'number' : 'null';

after being invoked on Number.prototype.

AFAICS, that leaves only one option: backing out of this spec change.

(See for the

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