HTML and CSS Reference
In-Depth Information
EXAMPLE
17.14 (
CONTINUED
)
<script type="text/javascript">
//
Negation within a Character Class
1
var reg_expression = /[^0-9]/;
2
var textString=prompt("Type a string of text","");
3
var result=reg_expression.test(textString)
;// R
eturns true
//
or false
document.write(result+"<br />");
if (result){
document.write("<b>The reg_ex /[^0-9]/ matched the
string\""+ textString +"\".<br />");
}
else{
alert("No Match!");
}
</script>
</body>
</html>
EXPLANATION
1
The caret inside a character class, when it is the first character after the opening
bracket, creates a negation, meaning any character not in this range. This regular
expression matches a string that
does not
contain a number between 0 and 9.
2
User input is assigned to the variable
textString
. In this example,
abc
was entered.
3
The regular expression
test()
method will return
true
because the string
abc
does
not contain a character ranging from 0 to 9 (see Figure 17.15).
Figure 17.15
The user entered
abc
. It contains a character that is
not
in the range
between 0 and 9.
Metasymbols offer an alternative way to represent a character class. For example, instead
of representing a number as
[0-9]
, it can be represented as
\d
, and the alternative for rep-
resenting a nonnumber
[^0-9]
is
\D
. Metasymbols are easier to use and to type than
metacharacters.
