HTML and CSS Reference
In-Depth Information
where
value
is the value you want to test for being finite. Like the
isNaN()
function, the
isFinite()
function returns a Boolean value:
true
if the value is a finite number falling
within JavaScript's acceptable range, and
false
if the numeric value falls outside that
range or if the value is not a number at all.
A program that reports a run-time or logical error may have a mismatched data value;
you can use the
isFinite()
and
isNaN()
functions to determine the state of your
data values.
Specifying the Number Format
When JavaScript displays a numeric value, it stores that value to 16 digits of accuracy.
This can result in long numeric strings of digits being displayed by browsers. For exam-
ple, the code
var x = 1/3;
document.write(“x = “ + x);
causes the following text string to be written to the Web page:
x = 0.3333333333333333
In most cases, you don't need to display a calculated value to 16 digits. For example,
with currency values, you usually want to display results only to two decimal places. To
control the number of digits displayed by browsers, you can apply the method
value
.toFixed(
n
)
where
value
is the value or variable and
n
is the number of decimal places that should
be displayed in the output. The following examples show the
toFixed()
method applied
to different numeric values:
var testValue = 2.835;
testValue.toFixed(0) // returns “3”
testValue.toFixed(1) // returns “2.8”
testValue.toFixed(2) // returns “2.84”
Note that the
toFixed()
method limits the number of decimals displayed by a value and
converts the value into a text string. Also, the
toFixed()
method rounds the last digit in
an expression rather than truncating it.
