javascript IF on radio button value

I have a radio group, bill 3 radio buttons

I could ge the radio button value.

On the c value i want to do a javascript if() to validate the credit card fields only if radio button with the c value is selected
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leakim971Connect With a Mentor PluritechnicianCommented:
Check this :

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">
<html xmlns="">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<script language="javascript">
	function validate() {
		var tp = document.getElementsByName("typep");
		var checkIsSelected = tp[0].checked;
		var paypalIsSelected = tp[1].checked;
		var creditCardIsSelected = tp[2].checked;
		var creditCardNumberIsValid = validateCrediCardNumber(document.getElementById("cnumber"));
		var creditCardIsNotOK = !creditCardIsSelected || !creditCardNumberIsValid;
		if( creditCardIsSelected && creditCardIsNotOK ) {
			alert("Please enter a valid credit card number")
		return checkIsSelected || paypalIsSelected || !creditCardIsNotOK; 
	function validateCrediCardNumber(field) {
		// simple check here
		return field.value.length>0;
<form onsubmit="return validate();" action="#">
    <input type="radio" name="typep" value="a" />Check<br />
    <input type="radio" name="typep" value="b" />Paypal<br />
    <input type="radio" name="typep" value="c" />Credit card&nbsp;<input type="textbox" name="cnumber" id="cnumber" /><br />
    <input type="submit" value="Submit" />

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Gurvinder Pal SinghCommented:
@smares32371: not sure if you need this advice, but i would suggest that you go for a drop-down rather than radio buttons for this one. In this way, all you need to do is, check the value of one field.

Let me know if you code base for this.
Please no points for this comment of mine, since if @leak's reply works, he deserve all points :)
smares32371Author Commented:
leakim971: ok its working how do i validate the rest of the credit card fields, there is like 10 more
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smares32371Author Commented:
I just want to make sure that the credit card fields are filled in .
line 21 :
return field.value.length>0;

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we check the field have one char (>0)
if you want 10 charactere or more :
return field.value.length>=10;

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smares32371Author Commented:
I meant I want 2 other fields to give alerts if they not filled in
close the question, award points (or not), try to understand the code, create a new question if you encounter difficulties
smares32371Author Commented:
i do understand the code but it only allows you to validate one field if the third radio button is selected lets forget about credit card fields, in general how would i validate normal fields base on the third button when there is more than one field.
what do you mean by validate ? Not empty ? Check the length propertie of its value (a string)

var myField_Value = document.getElementById( myField_ID ).value;
var myField_Is_Filled = myField_Value.length > 0; // this return true or false

with a field like this one :

<input type="text" id="myField_ID" name="myField_Name" />

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to validate multiple fields : return myField1_Is_Filled && myField2_Is_Filled && myField3_Is_Filled;
smares32371Author Commented:
yes not empty
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