This is jQuery plugin that helps submiting and validating your forms asynchronously. Keep your validation logic on server side, and for client side validate with javascript and AJAX.

Using ajaxForm plugin is fairly easy:

Just include plugin script into head section within script tag. And then call:

  $('#form').ajaxForm();

Optionaly ajaxFom function takes a hash of paratmeters:

  $('#form').ajaxForm({
    errorClass: 'error-field', // Error class applied to field if it failed validation
    showErrorMessage: true,    // Show error messages or just highlight field 
    errorMessageFormat: '<div class="error-message">{message}</div>', // Error message markup.
    insertMessage: 'before',   // Error message position. Accepts 2 options 'before' and 'after'
    onSuccess: function(){},     // Success callback. If validation passed
    onErrors: function(){},  //is callback for successfull server response with array of validation errors
    onError: function(){},  //is server error callback
  });

Or a single success callback function:

  $('#form').ajaxForm(function(){
    document.location.href = '/some_url';
  });

Optionaly you can specify redirect option in server response. So if JSON response contains redirect: '/some_url' it would be automaticaly triggered without any additional callbacks or configuration

In order to make ajaxForm correctly apply validation errors to form, server should respond with JSON containing errors in speified format.

  {errors: {email: "Invalid email format", username: "Username is already taken"}}

Multiple errors can be specified to the same field. But only the first one will be shown as an error message.

  {errors: {phone: ["Phone is too short", "Phone should be in numeric format"]}}

If you are using Rails, generating error hash is as simple as:

  render :json => {:errors => @model.errors}