validate.js

validate.js is a lightweight JavaScript form validation library inspired by CodeIgniter.

Features

Validate form fields from over a dozen rules
No dependencies
Customizable Messages
Supply your own validation callbacks for custom rules
Chainable customization methods for ease of declaration
Works in all major browsers, (even IE6!)
Modeled off the CodeIgniter form validation API

How to use

    var validator = new FormValidator('example_form', [{
        name: 'req',
        display: 'required',
        rules: 'required'
    }, {
        name: 'alphanumeric',
        rules: 'alpha_numeric'
    }, {
        name: 'password',
        rules: 'required'
    }, {
        name: 'password_confirm',
        display: 'password confirmation',
        rules: 'required|matches[password]'
    }, {
        name: 'email',
        rules: 'valid_email'
    }, {
        name: 'minlength',
        display: 'min length',
        rules: 'min_length[8]'
    }, {
        names: ['fname', 'lname'],
        rules: 'required|alpha'
    }], function(errors) {
        if (errors.length > 0) {
            // Show the errors
        }
    });