Till Schneidereit (2013-05-31T11:33:17.000Z)
github at esdiscuss.org (2013-07-12T02:27:21.467Z)
I couldn't find any precise definition for the spec term "present", so this is not entirely clear to me. Example: In step 7 of 15.4.3.21 Array.prototype.reduce, a TypeError must be thrown if the optional argument `initialValue` isn't present. If a value of `undefined` does *not* cause the argument to be present, that function can be implemented with the following signature: `function ArrayReduce(callbackfn, initialValue = undefined)` If, however, the value `undefined` means that the argument is present, the signature should probably be: `function ArrayReduce(callbackfn, ...rest)` The question isn't entirely academic, as I'm trying to get the self-hosted implementations of builtins in SpiderMonkey to be as close to the spec as possible.