form validation? & this.focus() & regular expressions?

[paulsjv]

Newbie here to JS so please be kind!

2 things.

1. I'm trying to write a function that will validate form input so below is what I have so far. Is there a better way to do this? Also, in the code below when a user doesn't input the correct information I want to set the cursor's focus back on the incorrect field but for some reason it is not doing this.

2. I'm also trying to validate and email address with a simple regular expression. The function I'm using is below but I get the following error in my JS console:

Error: invalid quantifier *@\w+([\.-]?\w+)*(\.\w{2,3})+$
Source File: http://localhost/project/js/registra..._validation.js
Line: 127, Column: 10
Source Code:
var re = /^\w+([\.-]?\w+*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;

 window.onload = setup_validation;
 var theForm;
 var submitBtn;
 var errorMsg;
 
 function setup_validation() {
 	if (document.getElementById) {
 		errorMsg = document.getElementById("error");
 		theForm = document.getElementById("theForm");
 		for (var i=0; i<theForm.length; i++) {
 			//alert(theForm.elements[i].id);
 			theForm.elements[i].onchange = validate_field;
 			if (theForm.elements[i].id == "submit") {
 				//alert(theForm.elements[i].id);
 				submitBtn = theForm.elements[i];
 				submitBtn.disabled = true;	
 			}
 		}
 	}
 	return false;
 }
 
 function validate_field() {
 	// some how display error messages maybe in a new "error" div?
 	//submitBtn.disabled = false;
 	
 	switch (this.id) {
 		case "username":
 			//alert(this.id);
 			//alert(this.value);
 			if (!check_length(this.value, 6)) {
 				this.style.backgroundColor = "#ff9";
 				this.focus();
 				//alert(this.id.focus() + " = focus | " + this.id + " | " + this.value);
 				errorMsg.innerHTML = "Username has to be 6 characters or more!";
 				return false;
 			} else {
 				this.style.backgroundColor = "#fff";
 				errorMsg.innerHTML = "";
 			}
 			// check to see if the form fields are 
 			break;
 		case "email":
 			alert(this.id);
 			alert(this.value);
 			if (!check_length(this.value, 0)) {
 				this.style.backgroundColor = "#ff9";
 				this.focus();
 				errorMsg.innerHTML = "Email can not be empty!";
 				return false;
 			} else {
 				this.style.backgroundColor = "#fff";
 				errorMsg.innerHTML = "";
 			}
 			
 			if (!validate_email(this.value)) {
 				this.style.backgroundColor = "#ff9";
 				this.focus();
 				errorMsg.innerHTML = "Please enter a valid email (e.g. test@test.com)";
 				return false;
 			} else {
 				this.style.backgroundColor = "#fff";
 				errorMsg.innerHTML = "";
 			}
 			break;
 		case "passwd1":
 			//alert(this.id);
 			//alert(this.value);
 			if (!check_length(this.value, 6)) {
 				this.style.backgroundColor = "#ff9";
 				this.focus();
 				errorMsg.innerHTML = "Your password has to be more than 6 characters!";
 				return false;
 			} else {
 				this.style.backgroundColor = "#fff";
 				errorMsg.innerHTML = "";
 			}
 			break;
 		case "passwd2":
 			//alert(this.id);
 			//alert(this.value);
 			if (!check_length(this.value, 6)) {
 				this.style.backgroundColor = "#ff9";
 				this.focus();
 				errorMsg.innerHTML = "Your password has to be more than 6 characters!";
 				return false;
 			} else {
 				this.style.backgroundColor = "#fff";
 				errorMsg.innerHTML = "";
 			}			
 			break;
 		default:
 			//alert("default");
 			break;
 	}
 
 	// if script has gotten here it has pasted all the test?
 	// check to see if we need to enable the submit button
 	// submit should be enabled when all required form fields are filled
 	// out and error free!  Is this the correct place to check? hm.
 	for (var i=0; i<theForm.length; i++) {
 		//alert(theForm.elements[i].value + " = elem value - " + theForm.elements[i].id + " = elem id");
 		if (theForm.elements[i].value.length <= 0) {
 			submitBtn.disabled = true;
 			break;
 		} else {
 			submitBtn.disabled = false;	
 		}
 	}	
 }
 
 function check_length(field, length) {
 	if (field.length < length) {
 		return false;
 	}
 	return true;
 }
 
 function validate_email(email) {
 	var re = /^\w+([\.-]?\w+*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;
 	alert(re + " | " + re.test(email) + " | " + email);
 	return re.test(email);
 }
 
 function validate_passwords(passwd1, passwd2) {
 		if (passwd1 != passwd2) {
 			return false;
 		}
 		return true;	
 }

[mortimer]

The Regular Expression error is because there was a bracket missing it should be
^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+