HTML and CSS Reference
In-Depth Information
EXAMPLE
17.30
<html>
<head><title>The Word Boundary</title></head>
<body>
<script type="text/javascript">
//
Anchoring a word with \b
1
var reg_expression = /\blove\b/;
var textString=prompt("Type a string of text","");
2
var result=reg_expression.test(textString)
;//
Returns true
//
or false
document.write(result+"<br />");
if (result){
document.write("<b>The regular expression /\blove\b/
matched the string \""+ textString +"\".<br />");
}
else{
alert("No Match!");
}
</script>
</body>
</html>
EXPLANATION
1
The regular expression contains the
\b
metacharacter, representing a word bound-
ary, not a specific character. The expression reads: Find a word beginning and
ending with
love
. This means that
gloves, lover, clover,
and so on, will not be found.
2
The regular expression
test()
method will return
true
because the string
love
is
within word boundary anchors
\b
. See Figure 17.32.
Figure 17.32
The user entered
Iloveyou!
. The word
love
is between word
boundaries (
\b
). The match was successful.
Alternation allows the regular expression to contain alternative patterns to be matched;
for example, the regular expression /
John|Karen|Steve
/ will match a line containing
John
or
Karen
or
Steve
. If
Karen, John
, or
Steve
are all on different lines, all lines are matched.
Each of the alternative expressions is separated by a vertical bar (the pipe symbol,
|
) and
the expressions can consist of any number of characters, unlike the character class that
only matches for one character; thus,
/a|b|c/
is the same as
[abc]
, whereas
/ab|de/
cannot
