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Comment by Cyberdog | Hacker News Reader

I didn't know JS had `??` for a nil coalescing operator, or, more specifically, I thought it already had `||` for that purpose, since I've been using it for that for a decade or so without any problems. How do the two differ?

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?? - returns right side operand if left side operand is null or undefined

|| - returns right side operand if left side operand is any falsy value

I like this answer because it’s practical. Eg score 0 is a different thing from score undefined (which means you don’t know the score).

I think ?? only acts on null or undefined, || acts on any falsey value.

?? only coalesces nullish values (hence the name), which only includes null and undefined. || coalesces falsey values, which include false, 0, and empty strings. || might work most of the time, but it requires extra checks when falsey values are valid.

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