The Assignment Operator (ActionScript: The Definitive Guide)

5.2. The Assignment Operator

identifier = expression

x = 4;                  // Assign 4 to the variable x
x = y;                  // Assign the value of y to the variable x
name = "dj duong";      // Assign a string to the variable name
products[3] = "Flash";  // Assign a string to the 4th element of products

// Assign a number to the area property of square
square.area = square.width * 2;

We may also perform multiple assignment operations at once, like this:

x = y = 4;  // Set both x and y to 4

Remember that assignment operations have right-to-left associativity, so 4 is assigned first to y then the value of y (which is now 4) is assigned to x.

5.2.1. Combining Operations with Assignment

Assignment operations are often used to set a variable's new value based in part on its old value. For example:

counter = counter + 10;             // Add 10 to the current value of counter
xPosition = xPosition + xVelocity;  // Add xVelocity to xPosition
score = score / 2;                  // Divide score by two

ActionScript supports a shorthand version of assignment, called compound assignment that combines operators such as +, -, / with the assignment operator to form a single "calculate-while-assigning" operation. So, to combine addition with assignment we use +=. To combine division with assignment, we use /=. The previous examples, hence, can be written more succinctly with compound assignment operators as follows:

counter += 10;
xPosition += xVelocity;
score /= 2;

Refer to Table 5-1 for a list of the compound assignment operators.


5. Operators		5.3. Arithmetic Operators