JavaScript tutorial:
|| Operator

 

The (||) operator is use to perform a logical disjunction on two expressions.

Syntax

result = expression1 || expression2

The || operator syntax has these parts:

Part Description
result Any variable.
expression1 Any expression.
expression2 Any expression.

Example

If either or both expressions evaluate to True, result is True. The following table illustrates how result is determined:

If expression1 is

And expression2 is

The result is

True

True

True

True

False

True

False

True

True

False

False

False

For information on when a run-time error is generated by the && operator, see the Operator Behavior table.

JavaScript uses the following rules for converting non-Boolean values to Boolean values:

  • All objects are considered true.

  • Strings are considered false if and only if they are empty.

  • null and undefined are considered false.

  • Numbers are false if, and only if, they are 0

See also: Operator Behavior, Operator Precedence, Operator Summary