this post was submitted on 23 Jan 2024
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submitted 10 months ago* (last edited 10 months ago) by [email protected] to c/programming_horror
 

For those unfamiliar with JS: subValue (the first argument in the forEach callback) is the value contained at arr[index].

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[–] [email protected] 11 points 10 months ago* (last edited 10 months ago) (1 children)

Trivially, could also just be a retVal.map(self.cleanupMetadata)

[–] [email protected] 16 points 10 months ago* (last edited 10 months ago)

But it can't! (Maybe)

calling map(obj.func) will pass func but won't set the this parameter correctly. If the called method uses this you will have a bad time.

The code you actually want would be retval.map(v => self.cleanupMetadata(v)) or the old-skool retval.map(self.cleanupMetadata.bind(self)).

Also the first version reuses the Array which may be important, but even if not will likely result in better performance. (Although this is likely mitigated by making the array polymorphic depending on the return type of cleanupMetadata and the overhead of forEach vs map.)

Wow, isn't JS a great language.

[–] [email protected] 7 points 10 months ago (1 children)

Entire block could literally be replaced with arr[index] = self.cleanupMetadata(subValue).

[–] charolastra 4 points 10 months ago (1 children)
[–] [email protected] 9 points 10 months ago

Figuratively the block could be replaced with a roll of duct tape and some chewing gum.