HTML and CSS Reference

In-Depth Information

EXAMPLE
5.5

<html>

<head><title>Auto-increment and Auto-decrement</title></head>

<body>

<h3>

<script type="text/javascript">

1

var x=5;

var y=0;

2

y = ++x;
//
add one to x first; then assign to y

document.write("Pre-increment:<br />");

3

document.write("y is " + y + "<br />");

document.write("x is " + x + "<br />");

document.write("-----------------------<br />");

4

var x=5;

var y=0;

5

y=x++;

//
assign value in x to y; then add one to x

document.write("Post-increment:<br />");

6

document.write("y is " +
y
+ "<br />");

document.write("x is " +
x
+ "<br />");

</script>

</h3>

</body>

</html>

EXPLANATION

1

The variables,
x
and
y
, are initialized to
5
and
0,
respectively.

2

The pre-increment operator is applied to
x
. This means that
x
will be incremented

before
the assignment is made. The value of
x
was
5
, now it is
6
. The variable
y
is

assigned
6. x
is
6
,
y
is
6
.

3

The new values of
y
and
x
are displayed in the browser window.

4

The variables
x
and
y
are assigned values of
5
and
0,
respectively.

5

This time the post-increment operator is applied to
x
. This means that
x
will be

incremented
after
the assignment is made. The number
5
is assigned to the vari-

able
y
, and then
x
is incremented by
1
. So
x
is
5
and
y
is
6
.

6

The new values of
y
and
x
are displayed in the browser window. See Figure 5.5.