Form Validation

I have some form validation done, but it's not very good. How do i make sure that users can only use a-z, A-Z, 0-9. (there for users would not be able to use special characters) - note: i have the php server side validation done but i want javascript also, thanks

Here is the code i have so far:

function validate_username(field,alerttxt)
	{
		with (field)
			{
				numofchar=value.length;
				if (numofchar<5) 
					  {alert(alerttxt);return false}
				else {return true}
			}
	}

HTML:

function validate_form(thisform)
{
	with (thisform)
	{

if (validate_username(username,"Ooops... Username must be at least 5 characters in length")==false)
		  {username.focus();return false}

HTML:

how can i make sure that the $username only can have a-z, A-Z, 0-9

 

if (numofchar<5 || value.match(/[^a-z0-9]/i))

Code (markup):

Also, you might want to update the message so it informs of this new check.

 

How can i change this line around so that

if (numofchar<5 || value.match(/[^a-z0-9]/i))

HTML:

The rules are:
between 5 and 15 characters
a-z A-Z 0-9 characters only

thanks for your help

 

It's the same pattern as I gave you here.

http://forums.digitalpoint.com/showthread.php?t=370927

if (!value.match(/^[a-z0-9]{5,15}$/i))
{
    // Error
}

Code (javascript):

 

Sorry, i'm new to all of this, i didn't think you could use the same format in Javascript as you could in PHP. Thanks a million nico_swd, your a big help, thanks

 

No problem.

 

Sorry, i'm after running into a bit of a problem. If i use

if (!value.match(/^[a-z0-9]{5,15}$/i))

HTML:

If a users name is O'Neill it wont accept it becaue of the ' character in the name.

How do i just change the if statement to only check if its {5,15} or is their a way that i can inlude certain character such as ' and , and -

 

Add them to the list inside [ and ]. Usually it will work except in a few cases. e.g. a hyphen has to be escaped or at the end of the list:

if (!value.match(/^[a-z0-9',-]{5,15}$/i))

Code (markup):