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/*
JavaScript: A Beginner's Guide, Second Edition
By John Pollock
Publisher: McGraw-Hill,
Published December 2003, 550 pages,
ISBN 0072227907
*/
<HTML>
<HEAD>
<SCRIPT language="JavaScript">
<!--
function check_it()
{
var theurl=document.f1.t1.value;
var tomatch= /http:\/\/[A-Za-z0-9\.-]{3,}\.[A-Za-z]{3}/
if (tomatch.test(theurl))
{
window.alert("URL OK.");
return true;
}
else
{
window.alert("URL invalid. Try again.");
return false;
}
}
//-->
</SCRIPT>
</HEAD>
<BODY>
<FORM name="f1" action="#" onSubmit="return check_it();">
Enter URL:<BR>
<INPUT type="text" name="t1">
<BR>
<INPUT type="submit" value="Submit">
</BODY>
</HTML>
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