Question

I have the following code as part of my email validation script. I’d like to learn more about the variable reg but don’t know how to find relevant information because I do not know what the syntax is called. Could someone direct me to the proper resource or tell me the name of this type of syntax?

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;
   }
}

Answer 1

It’s called a regular expression.

There are a lot of resources on regexes, and particularly about regexes in JS. Here is a guide that explains how to use them:

http://www.javascriptkit.com/javatutors/re.shtml

and a guide to the patterns themselves:

http://www.javascriptkit.com/javatutors/redev2.shtml