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isError only identifies literal errors when extending Error and targeting IE #2509

michaeldjeffrey opened this Issue Nov 29, 2018 · 2 comments


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michaeldjeffrey commented Nov 29, 2018



Reproduction link

Steps to reproduce

Make a custom error using the class-extends syntax.
Throw error during a route transition.

What is expected?

Error is caught and sent to Router.onError handler.

What is actually happening?

Error is being identified as a plain object.

Have a custom error to carry notifications with uncaught errors in an application.
No notifications were showing up in production where we support IE11.
The custom error correctly identifies as an instanceof Error, but the util/isError function deems it an object.

I'm currently using some snippets from to get the Error prototype on my custom error.


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@posva posva closed this Nov 30, 2018


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michaeldjeffrey commented Nov 30, 2018

You are correct. I updated my babel packages and everything works fine now.
I must have been in that weird error vortex where I did the same thing on the babeljs website and it wasn't working for me. But today, lo and behold.

Thanks, and sorry @posva

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