input field restricting to numbers only

This page shows a technique for restricting the field to just numbers. The script also allows you to automatically jump to the next field if the user presses the decimal key.

Put this JavaScript to head tag in your HTML page

<script type="text/javascript">
<!--
function numbersonly(inputfield, e, dec) {
	var key;
	var keychar;
	if (window.event)
		key = window.event.keyCode;
	else if (e)
		key = e.which;
	else
		return true;
	keychar = String.fromCharCode(key);
	if ((key == null) || (key == 0) || (key == 8) ||
		(key == 9) || (key == 13) || (key == 27))
		return true;
	else if ((("0123456789").indexOf(keychar) > -1))
		return true;
	else if (dec && (keychar == ".")) {
		inputfield.form.elements[dec].focus();
		return false;
	}
	else
		return false;
}
//-->
</script>

Now, we will use our script in HTML form

<form action="/signup" method="post">
	<label>U.S. ZIP Code:</label><input type="text" name="zip" size="5" maxlength="5" value="" onKeyPress="return numbersonly(this, event)"/>
	<button type="submit">Submit</button>
</form>

• HTML
• CSS
• JavaScript

Validating a Credit Card Number with JavaScript

An easy way to validate credit card number with one function in JavaScript

function isValidCardNumber(cardNumber) {
	var nCheck = 0;
	var nDigit = 0;
	var bEven = false;

	for (n = cardNumber.length - 1; n >= 0; n--) {
		var cDigit = cardNumber.charAt(n);
		if (isDigit(cDigit)) {
			var nDigit = parseInt(cDigit, 10);
			if (bEven) {
				if ((nDigit *= 2) > 9)
					nDigit -= 9;
			}
			nCheck += nDigit;
			bEven = ! bEven;
		}
		else if (cDigit != ' ' && cDigit != '.' && cDigit != '-') {
			return false;
		}
	}
	return (nCheck % 10) == 0;
}
function isDigit(c) {
	var strAllowed = "1234567890";
	return (strAllowed.indexOf(c) != -1);
}
function isCardTypeCorrect(cardNumber, type) {
	var nLen = 0;
	for (n = 0; n < cardNumber.length; n++) {
		if (isDigit(cardNumber.substring(n, n + 1)))
			++nLen;
	}

	if (type == 'Visa')
		return ((cardNumber.substring(0, 1) == '4') && (nLen == 13 || nLen == 16));
	else if (type == 'Amex')
		return ((cardNumber.substring(0, 2) == '34' || cardNumber.substring(0, 2) == '37') && (nLen == 15));
	else if (type == 'Master Card')
		return ((cardNumber.substring(0, 2) == '51' || cardNumber.substring(0, 2) == '52'
			|| cardNumber.substring(0, 2) == '53' || cardNumber.substring(0, 2) == '54'
			|| cardNumber.substring(0, 2) == '55') && (nLen == 16));
	else
		return false;

}

• JavaScript
• Validation

Validate email address using JavaScript regular expression

Here is the code to validate email address in JavaScript using regular expression.

function validate(form_id,email) {
   var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
   var address = document.forms[form_id].elements[email].value;
   if(reg.test(address) == false) {
      alert('Invalid Email Address');
      return false;
   }
}

In the forms 'onsubmit' code call javascript:return validate('form_id','email_field_id')

<form id="form_id" method="post" action="action.php" onsubmit="javascript:return validate('form_id','email');">
   <input type="text" id="email" name="email" />
   <input type="submit" value="Submit" />
</form>

You should not rely purely on client side validation on your website / web application, if the user has javascript disabled this will not work. Always validate on the server.

• JavaScript
• Validation

JavaScript String Replace All

The JavaScript function for String Replace replaces the first occurrence in the string. The function is similar to the php function str_replace and takes two simple parameters. The first parameter is the pattern to find and the second parameter is the string to replace the pattern with when found. The javascript function does not Replace All...

str = str.replace("find","replace")

To ReplaceAll you have to do it a little differently. To replace all occurrences in the string, use the g modifier like this:

str = str.replace(/find/g,"replace")

• JavaScript