ActionScript for Flash MX: The Definitive Guide, Second Edition

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Chapter 5: Operators

Operator Associativity

As we’ve just seen, operator precedence indicates the pecking order of operators:

those with a higher precedence are executed before those with a lower precedence.

But what happens when multiple operators occur together and have the same level of

precedence? In such a case, we apply the rules of operator associativity, which indi-

cate the direction of an operation. Operators are either left-associative (performed

left to right) or right-associative (performed right to left). For example, consider this

expression:

a = b * c / d

The * and / operators are left-associative, so the * operation on the left (b * c)is

performed first. The preceding example is equivalent to:

a = (b * c) / d

instanceof 10 left to right check an object’s class

== 9 left to right equality

!= 9 left to right not equal to

=== 9 left to right strict equality

!= = 9 left to right strict inequality

& 8 left to right bitwise AND

^ 7 left to right bitwise XOR

| 6 left to right bitwise OR

&& 5 left to right logical AND

|| 4 left to right logical OR

?: 3 right to left conditional

= 2 right to left assignment

+= 2 right to left add and reassign

–= 2 right to left subtract and reassign

*= 2 right to left multiply and reassign

/= 2 right to left divide and reassign

%= 2 right to left modulo ...