Per https://tc39.github.io/ecma262/#sec-object.getownpropertydescriptor , `Object.getOwnPropertyDescriptor` will throw if you pass it `null` or `undefined` as the first argument, if you pass it something as the second argument that can't be coerced to a primitive (ie, a valueOf or toString throws, or both are missing), or if the object you pass is a Proxy (or other exotic object) whose `[[GetOwnProperty]]` trap throws or returns anything other than an Object or `undefined`.
On Wed, Jan 11, 2017 at 5:55 PM, Isiah Meadows <[email protected]> wrote: > I was expecting the error to throw on invoking the getter. Calling > `Object.getOwnPropertyDescriptor` > should *never* do that (spec invariant). > > On Wed, Jan 11, 2017, 15:30 Boris Zbarsky <[email protected]> wrote: > >> On 1/11/17 3:12 PM, Isiah Meadows wrote: >> > Okay. The error stack being constructed that early is odd, though. >> >> I'm not sure I follow. The error stack in SpiderMonkey and V8 (and >> JavaScriptCore too, afaict) is captured at the point when the Error >> object is created. The captured thing is information that can be used >> to construct a stack string later. >> >> Then getting .stack constructs the stack string. This operation is >> somewhat expensive, so is deferred until someone asks. >> >> In V8, the stringification process includes an explicit >> script-modifiable hook: the "prepareStackTrace" property of the Error >> constructor. >> >> Is the odd part the stack capture during Error object construction? >> Were you expecting it to only be captured at the throw point? >> >> -Boris >> > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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