A jQuery plugin for form validation. Use for e-mail, message text fields, as well as check boxes and radio buttons.

form-validation.js

/*General Purpose Form Validation*/


(function($) {
    $.fn.validateForm = function() {  
        var $form = $(this),   
            $submit = $form.find('button[type="submit"]'),
            $messages = $('.form-messages[data-target="'+$form.attr('id')+'"]'),
            successMessage = $form.attr('data-message'),
            $requiredFields = $form.find('[data-required="true"]'),
            requiredNum = $form.find('[data-required="true"]').length,
            $needsValidation = $form.find('[data-validate="true"]'),
            submittedFields=0,
            formIsValid=false;

        return this.each(function() {
           
            $needsValidation.add($requiredFields).each(function(){
                if ($(this).is('fieldset.radio-button-group')||$(this).is('fieldset.checkbox-group')) {
                    // binding validation to .change() because blur doesn't work on radios or checkboxes
                    $(this).find('input').each(function(){
                        $(this).change(function(){
                            $(this).parents('fieldset').validateField(); 
                        });
                    });
                }else{
                    //binding validation to .blur 
                    $(this).blur(function(){
                        $(this).validateField();
                    });
                }
            }); 

            $submit.click(function(e){
                e.preventDefault();
                //clear out any error messages
                $messages.empty();
                
                $requiredFields.each(function(){
                    var $_this = $(this),
                    isValid= $_this.attr('data-valid');
                    if (isValid!=="true") {
                        $_this.validateField(); 
                    }else{
                        //keep track of how many required fields are valid
                        submittedFields++;
                    }
                });

                if (submittedFields==requiredNum) {
                    formIsValid=true;
                }

                $needsValidation.each(function(){
                    var $_this = $(this),
                    isValid= $_this.attr('data-valid');
                    if ($_this.val().length>0) {
                        $_this.validateField();
                        if (isValid!=="true") {
                            // if non-required fields are filled out and NOT valid, it invalidates the entire form
                            formIsValid=false;
                        }
                    }
                });

                if (formIsValid===true) {
                    $messages.append('<p class="confirmed">'+successMessage+'</p>');
                    /*submission script here*/
                }

            });

        });

    };
}(jQuery));

(function($) {
     
    $.fn.validateField = function() {  
        var $_this = $(this),        
            fieldName=$_this.attr('name'),
            counts,
            min = 1,
            max = 1000,
            validated = false,
            value=$_this.val(),
            $messages = $('.form-messages[data-target="'+$_this.parents('form').attr('id')+'"]'),
            message=$_this.attr('data-message');
            //if these attributes are defined, replace the defaults
            if ($_this.attr('data-min')) {min = parseInt($_this.attr('data-min'));}
            if ($_this.attr('data-max')) {max = parseInt($_this.attr('data-max'));}
            if (!fieldName) {fieldName=$_this.attr("id");} //fieldsets won't have names, so use IDs, this is used for messages

        return this.each(function() {
                //begin validation form elements
                $('.'+fieldName+'-message').remove();
                if ($_this.is('fieldset.checkbox-group')===true) {
                    counts=$_this.find('input:checkbox:checked').length;
                    //check to see if the number of checkboxes fall within range defined by min and max
                    if (counts>min&&counts<=max) {
                        validated=true; 
                    }
                }
                if ($_this.is('fieldset.radio-button-group')===true) {
                    counts=$_this.find('input:radio:checked').length;
                    if (counts==1) {
                        validated=true; 
                    }
                }
                if ($_this.is('select')===true) {
                    if (value.length>0) {
                        validated=true;
                    }
                }
                if ($_this.is('input')===true) {
                    var type = $_this.attr('type'); 
                    if (type=="text") {
                        if (fieldName=="email") {
                            var pattern = /^(([A-Za-z0-9]+_+)|([A-Za-z0-9]+\-+)|([A-Za-z0-9]+\.+)|([A-Za-z0-9]+\++))*[A-Za-z0-9\-]+@((\w+\-+)|(\w+\.))*\w{1,63}\.[a-zA-Z]{2,6}$/i;
                            var isEmail;
                            isEmail = pattern.test(value);
                            if (isEmail===true) {
                                validated=true;
                            }
                        }else{
                          if (value.length>0){
                            validated=true;
                          }
                        }
                    }
                }
                if ($_this.is('textarea')) {
                    if (value.length > min && value.length <= max ) {
                        validated=true;
                    }
                }
                //END validation form elements
                
                //added error classes
                if (validated===false) {
                    $messages.append('<p class="'+fieldName+'-message">'+message+'</p>');
                    if ($_this.is('fieldset')){
                        $_this.addClass('missing');
                    }else{
                        $_this.parent().addClass('missing');
                    }
                    $_this.removeAttr('data-valid');
                }else{
                    $_this.removeClass('missing');
                    $_this.parent().removeClass('missing'); //for fieldsets
                    $_this.attr('data-valid','true');
                }
        });
    };
}(jQuery));