Truthfulness of empty arrays in Javascript… that’s not cool!


An empty array when cast to Boolean evaluates true, indicating that it is truthy.

Boolean([])
true

An empty array compared to true evaluates false, indicating that it is not truthy.

[] == true
false
[] == false
true

And yet the Boolean opposite of an empty array still evaluates false, implying that the empty array is truthy.  What’s an interpreter to do?

![]
false
!![]
true

Just some more contradictory anecdotal evidence to help drive you mad.

Boolean([]) == []
false
Boolean([]) == ![]
false
Boolean([]) == !![]
true
!Boolean([]) == []
true

Conclusion?  I’ll just bit my tongue this time.

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About andyortlieb

I often find myself figuring out some niche oddities, only to find myself stuck on those same problems a year later due to my wide yet thin activity in certain topics related to my career and hobbies. This blog is where I document these nuances (or nuisances) to ease my pain the second time around, and hopefully that of some other fellow desperate internet scouts.
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