what is the usage for logical ! before function in javascript

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what is the usage for logical ! before function in javascript

Asked by Norton Alex

at 2025-02-01 21:15:33

Point:500 Replies:2 POST_ID:829294USER_ID:12423

Topic:

javascript

I have seen a lot javascript file whcih starting with "!" character before function

What is the purpose of that ?

For example;

!function(x){a=x}()

Please advise

Accepted Solution

Expert: Wilson Edwards replied at 2025-02-01 21:21:10

500 points Excellent

Reference:

https://www.sololearn.com/en/Discuss/2019535/what-s-meaning-the-symbol-before-a-function-return-something-different

https://www.sololearn.com/en/compiler-playground/Wt2b0KJCm2kS/?ref=app

More detail:

https://stackoverflow.com/questions/3755606/what-does-the-exclamation-mark-do-before-the-function

Expert: Wilson Edwards replied at 2025-02-01 21:19:31

! is the boolean not operator, which you probably know. Calling a function results in a value (in this case undefined). The side effect still happens, so a will be assigned 7, but then nothing happens. You can rewrite it like this:a = x;!undefined!undefined is true, but since it isn't used at all, it won't matter.

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