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 runtime error is generated by the && operator, see the Operator Behavior table.
JavaScript uses the following rules for converting nonBoolean 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 