What does !+ mean in Javascript?

Question

After taking over a project from someone else, written in Javascript. One line I see everywhere is if statements using !+msg. From testing I can see that it checks to see if there is more than one word or not, but I was hoping someone could explain why this works. Thanks!

It's difficult to give a contextually informative answer because nobody knows what sort of value msg might contain, or why. — Pointy
– Pointy, Commented Apr 6, 2020 at 18:16

Pointy · Accepted Answer · 2020-04-06 18:15:19Z

8

The + operator coerces its operand to a number, and the ! operator coerces its operand to a boolean value and inverts its sense (false -> true or vice-versa). Thus !+msg means, "if the value of msg interpreted as a number is 0 or NaN, the value should be true, otherwise false."

answered Apr 6, 2020 at 18:15

Pointy

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Bread Over a year ago

Makes sense! Thank you!

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