Performs a logical conjunction on two expressions.
expression1 && expression2 
Arguments
 expression1

Any expression.
 expression2

Any expression.
Remarks
If, and only if, both expressions evaluate to true, the result is true. If either expression evaluates to false, the result is false. The following table illustrates how the result is determined:
If expression1 coerces to

And expression2 coerces to

The result is  The result coerces to 

true 
true 

true 
true 
false 

false 
false 
true 

false 
false 
false 

false 
JScript 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.