...
 The If Instruction evaluates an expression from a predicate and returns a boolean value
true
orfalse
.  Therefore Boolean algebra is applied, e.g. to evaluate expressions such as
$returnCode.toNumber == 0
.  For details see JS7  Expressions for Variables
Binary Operations
 The If Instruction knows of two binary operations, which are and (conjunction) and or (disjunction) with the syntax
&&
and
.Possible operations correspond to the following matrix:
x y x && y x  y false false false false true false false true false true false true true true true true  Round brackets should be used to group multiple expressions and to control the order of evaluation.
 Conjunction beats disjunction if no grouping is used, i.e.

x && y  z
is the same as(x && y)  z

x  y && z
is the same asx  (y && z)

 Both operations using the basic elements
true
,false
cover a number of algebraic laws such as associativity, commutativity and distributivity. For more details see Wikipedia.
...