Check Error In Javascript
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here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about http://stackoverflow.com/questions/30469261/checking-for-typeof-error-in-js Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up checking for typeof error in JS up vote 12 down vote favorite 1 In javascript error JS it doesn't seem possible to check if an argument passed to a function is actually of the type 'error' or an instance of Error. For example, this is not valid: typeof err === 'error' since there are only 6 possible types (in the form of strings): The typeof operator returns type information as a string. There are six possible values that typeof returns: "number," "string," "boolean," "object," "function," and "undefined." javascript error check MSDN But what if I have a simple use case like this: function errorHandler(err) { if (typeof err === 'error') { throw err; } else { console.error('Unexpectedly, no error was passed to error handler. But here is the message:',err); } } so what is the best way to determine if an argument is an instance of Error? is the instanceof operator of any help? javascript node.js share|improve this question edited May 26 '15 at 21:31 asked May 26 '15 at 21:27 Alex Mills 4,39672581 1 Yes, use err instanceof Error –colecmc May 26 '15 at 21:31 1 @colecmc won't that be problematic if the error might have come from code in a frame or another window? In that case there will be different prototype Error objects, and instanceof won't work as expected. (see developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…) –Doin Aug 30 at 10:30 @Doin, I don't think so. It will just validate the actual error object. –colecmc Aug 30 at 17:50 @colecmc, I think you'll find that if you've thrown err in (say) an iframe, but then pass it to the parent window for handing, you'll get (err instanceof Error) === false. That's because the iframe and its parent window have distinct, different Error object prototypes. Simil