Is there any way in JavaScript to throw an error when I'm trying to access non existent object property?
inst.prop //Error
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1Possible duplicate of stackoverflow.com/questions/6511542/…Rakesh_Kumar– Rakesh_Kumar2015-02-04 08:25:44 +00:00Commented Feb 4, 2015 at 8:25
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3 Answers
Not presently, no, not on the object itself. ES2015+ offers proxies, and if you wrap the object in a proxy, you can then have the proxy throw an error when you try to read a property through the proxy that the underlying object doesn't have. But that would require wrapping in a proxy, and would require ES2015 support in the environment you're using (proxies can't be polyfilled). All up-to-date major JavaSript engines support proxies. If you're doing this on the web, the engines in slightly older browsers (IE11 for instance) don't support proxies and they cannot be polyfilled.
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The zealit Node package provides a way to that:
const zealit = require('zealit')
const ref = { foo: true, bar: undefined }
const zealed = zealit(ref)
zealed.prop // => will raise an error
1 Comment
T.J. Crowder
Right. Because it uses proxies, as I discussed in my answer.
I'm not advanced or well-read enough to speak on the use of proxies. If I needed this type of functionality, I would opt to create a class with private properties and a getter method. The getter method would throw an error if an invalid key was passed.
1 Comment
Gerardo Perrucci
You can check the documentation here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…