How does !!~ (not not tilde/bang bang tilde) alter the result of a ‘contains/included’ Array method call?

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There’s a specfic reason you’ll sometimes see ~ applied in front of $.inArray.

Basically, 

~$.inArray("foo", bar)

is a shorter way to do

$.inArray("foo", bar) !== -1

$.inArray returns the index of the item in the array if the first argument is found, and it returns -1 if its not found. This means that if you’re looking for a boolean of “is this value in the array?”, you can’t do a boolean comparison, since -1 is a truthy value, and when $.inArray returns 0 (a falsy value), it means its actually found in the first element of the array.

Applying the ~ bitwise operator causes -1 to become 0, and causes 0 to become `-1. Thus, not finding the value in the array and applying the bitwise NOT results in a falsy value (0), and all other values will return non-0 numbers, and will represent a truthy result.

if (~$.inArray("foo", ["foo",2,3])) {
    // Will run
}

And it’ll work as intended.

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