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7.4.27 Logical NOT Operator (!)

Used to perform logical negation on an expression.
 

Syntax

result = !expression

Arguments

result
Any variable.
expression
Any expression.

Remarks

The following table illustrates how result is determined.
 

If expression is 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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