HTML and CSS Reference
In-Depth Information
A character class represents
one
character from a set of characters. For example
[abc]
matches either an
a
,
b
,
or
c;
and
[a-z]
matches one character from a set of characters in
the range from
a
to
z
; and
[0-9]
matches one character in the range of digits between
0
to
9
. If the character class contains a leading caret, ^, then the class represents any one
character not in the set; thus,
[^a-zA-Z]
matches a single character
not
in the range from
a
to
z
or
A
to
Z
, and
[^0-9]
matches a single digit not in the range between 0 and 9.
JavaScript provides additional symbols, called metasymbols, to represent a character
class. The symbols
\d
and
\D
represent a single digit and a single nondigit, respectively;
the same as
[0-9]
and
[^0-9]
; whereas
\w
and
\W
represent a single word character and
a single nonword character, respectively; same as
[A-Za-z_0-9]
and
[^A-Za-z_0-9]
.
EXAMPLE
17.12
<html>
<head><title>The Character Class</title></head>
<body>
<script type="text/javascript">
1
var reg_expression = /[A-Z][a-z]eve/;
2
var textString=prompt("Type a string of text","");
3
var result=reg_expression.test(textString)
;//
Returns true
//
or false
document.write(result+"<br />");
if ( result){
document.write("<b>The reg_ex /[A-Z][a-z]eve/ matched the
string\""+ textString +"\".<br />");
}
else{
alert("No Match!");
}
</script>
</body>
</html>
EXPLANATION
1
The variable is assigned a bracketed regular expression containing alphanumeric
characters. This regular expression matches a string that contains at least one up-
percase character ranging between A and Z, followed by one lowercase character
ranging between a and z, followed by
eve
.
2
The variable
textString
is assigned user input, in this example
Steven lives in Cleve-
land
was entered.
3
The regular expression
test()
method will return
true
because
Steven
contains an
uppercase character, followed by a lowercase character, and
eve
.
Cleveland
also
matches the pattern. The variable
result
contains either
true
or
false
. See the out-
put in Figures 17.12 and 17.13.