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/*
JavaScript Unleashed, Third Edition
by Richard Wagner and R. Allen Wyke
ISBN: 067231763X
Publisher Sams CopyRight 2000
*/
<html>
<head>
<title>Credit Card Validation</title>
<script language="JavaScript">
<!--begin script
function isCreditCard(textObj) {
/*
* This function validates a credit card entry.
* If the checksum is ok, the function returns true.
*/
var ccNum;
var odd = 1;
var even = 2;
var calcCard = 0;
var calcs = 0;
var ccNum2 = "";
var aChar = '';
var cc;
var r;
ccNum = textObj.value;
for(var i = 0; i != ccNum.length; i++) {
aChar = ccNum.substring(i,i+1);
if(aChar == '-') {
continue;
}
ccNum2 = ccNum2 + aChar;
}
cc = parseInt(ccNum2);
if(cc == 0) {
return false;
}
r = ccNum.length / 2;
if(ccNum.length - (parseInt(r)*2) == 0) {
odd = 2;
even = 1;
}
for(var x = ccNum.length - 1; x > 0; x--) {
r = x / 2;
if(r < 1) {
r++;
}
if(x - (parseInt(r) * 2) != 0) {
calcs = (parseInt(ccNum.charAt(x - 1))) * odd;
}
else {
calcs = (parseInt(ccNum.charAt(x - 1))) * even;
}
if(calcs >= 10) {
calcs = calcs - 10 + 1;
}
calcCard = calcCard + calcs;
}
calcs = 10 - (calcCard % 10);
if(calcs == 10) {
calcs = 0;
}
if(calcs == (parseInt(ccNum.charAt(ccNum.length - 1)))) {
return true;
}
else {
return false;
}
}
// end script-->
</script>
</head>
<BODY>
<h1>Credit Card Validation</h1>
<form name="form1">
<input type="text"
size=16
maxlength=16
name="data">
<input type="button"
name="CheckButton"
value="Validate"
onClick="document.form1.result.value = '' +
isCreditCard(document.form1.data)">
<br>
Result <input type="text"
size=16
maxlength=16
name="result">
</form>
</body>
</html>
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