Dynamic HTML: The Definitive Reference

Name

- - — NN 2 IE J1 ECMA 1

Synopsis

The decrement operator. This unary operator subtracts 1 from the current value of a variable expression. You can place the operator in front of or behind the variable for a different effect. When the operator is in front of the variable, the variable is decremented before it is evaluated in the current statement. For example, in the following sequence:

var a, b
a = 5
b = --a

one is subtracted from a before being assigned to b. Therefore, both b and a are 4 when these statements finish running. In contrast, in the following sequence:

var a, b
a = 5
b = a--

the subtraction occurs after a is assigned to b. When these statements complete, b is 5 and a is 4.

This behavior impacts the way for-loop-counting variables are defined and used. Typically, a loop counter that counts backwards from a maximum value decrements the counter after the statements in the loop have run. Thus most loop counters place the operator after the counter variable:

for (var i = 10; i >=0; i--) ...

Example

--n
n--