ActionScript for Flash MX: The Definitive Guide, Second Edition

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The Assignment Operator

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In contrast, the = (assignment) operator is right-associative, so the expression:

a = b = c = d

says, “assign d to c, then assign c to b, then assign b to a,” as in:

a = (b = (c = d))

Operator associativity is fairly intuitive, but if you’re getting an unexpected value

from a complex expression, consult Table 5-1 or add extra parentheses. We’ll note

cases in which associativity is a common source of errors throughout the remainder

of this chapter.

Datatypes and Operators

Some operators accept varying datatypes as operands. Depending on the datatype of

an operand, the effect of an operator may change. The

+ operator, for example, per-

forms addition when used with numeric operands, but it performs concatenation

when used with string operands. If operands are of different datatypes or of the

wrong type, ActionScript will perform type conversion according to the rules

described in Chapter 3, which can have serious effects on your code.

The remainder of this chapter offers reference-style descriptions of each ActionScript

operator. Newer programmers may wish to skim past topics that have not yet been

covered in detail.

The Assignment Operator

We’ve already used the assignment operator frequently. It can place a value into a

variable, array element, or object property. ...