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I haven't either, only that delete will cause code to be de-optimized.

Its main purpose is deleting a property from an object, which is a pretty slow operation on modern JS engines. Unless some code tests for the existence of a property, setting it to null is a better idea.

I'd suggest undefined over null if you want to effectively remove a property, since JSON.stringify won't serialize those properties... in an array, it will become null.

Though, I don't use delete much, I honestly don't worry about it much. In most contexts it's a bit of a premature optimization unless you are in a very low-level tool that will be used for example gaming, video or photo manipulation, there are probably better optimizations to make.

I think it affected earlier versions of IE - Douglas Crockford detailed an issue here:

http://javascript.crockford.com/memory/leak.html

What the hell is wrong with people today? I was hazarding a guess what was being referred to and I get down voted?

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