Logical NOT Operator (!)
Performs logical negation on an expression.
!expression
The following table illustrates how the result is determined.
| If expression coerces to | Then result is |
|---|---|
| true | false |
| false | true |
All unary operators, such as the ! operator, evaluate expressions as follows:
-
If applied to undefined or null expressions, a run-time error is raised.
-
Objects are converted to strings.
-
Strings are converted to numbers if possible. If not, a run-time error is raised.
-
Boolean values are treated as numbers (0 if false, 1 if true).
The operator is applied to the resulting number.
For the ! operator, if expression is nonzero, result is zero. If expression is zero, result is 1.
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