javascript validation for name,contact numbers - asp.net

Question

I have created 2 pages login and signup..On signup form I have used javascript for nonempty fields. Now I want to add validation for characters only, digits and date.
How to write these additional validations in my function. Please help. My code is:
<script type="text/javascript">
function Validateform() {
var Firstname = document.getElementById("txtfirst").value;
if (Firstname == "First Name" || Firstname == ""){
alert("Firstname must be filled out");
return false;
}
}
</script>
and I have called this function on onClientClick event of signup button.

Answer 1

Code to check alpha characters:
function onlyAlpha(inputtext){
var acceptedChars= /^[A-Za-z]+$/;
if(inputtext.value.match(acceptedChars)){
alert('ok');
return true;
} else {
alert('input alphabet characters only');
return false;
}
}
you can call this function on onblur on onClick with inputtext parameter as u wish to validate and the same way u can apply digits validation too.

Answer 2

There are n number of methods to validate name. Let me share my view
Method 1
First Name:
lname=document.getElementById('lname').value;
namelen=/^([a-zA-Z0-9]{5,15})+$/;
if(!namelen.test(lname))
{
alert('Enter a name');
return false;
}
else
{
document.getElementById('splname').innerHTML="";
}
returnValue;
}
Method 2 - To color the background
namelen=document.getElementById('lname').value.length;
lname=document.getElementById('lname').value;
if((namelen=<5 || namelen >=12) || !isNaN(lname))
{
document.getElementById('splname').innerHTML="Enter a name";
document.getElementById('lname').style.background="red";
document.getElementById('lname').focus();
}
else
{
document.getElementById('splname').innerHTML="";
document.getElementById('lname').style.background="green";
}
returnValue;
}
Method 3
fname=document.getElementById('fname').value;
namelen=/^([a-zA-Z0-9]{5,15})+$/;
if(!namelen.test(fname))
{
document.getElementById('spfname').innerHTML="Enter a name";
return false;
}
else
{
document.getElementById('spfname').innerHTML="";
}