Try testing the following form with valid and invalid email addresses. The

code uses javascript to match the users input with a regular expression.

函数代码：

复制代码 代码如下:

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')

使用方法：

复制代码 代码如下:

<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.

from:http://www.white-hat-web-design.co.uk/blog/javascript-validation/