gradual

Automated progressive enhancement for <form> elements when using Taunus

Note

Starting in taunus@7.0.0 this module is incorporated in core and enabled by default!

Install

npm install gradual --save

Setup

Use gradual.configure to give gradual a reference of your taunus object to set it up. You can also set a qs option that will be used to construct a query string appended to each AJAX form request.

gradual.configure({
  taunus: taunus,
  qs: function (form) {
    return {
      foo: 'bar'
    };
  }
});

Usage

Gradual is a progressive enhancement facility for Taunus that allows you to seamlessly submit plain old HTML forms via AJAX and handle the response in a conventional manner.

Gradual exposes an event emitter that has three additional methods.

gradual.hijack(e)

Exactly as you would expect, this method will submit a <form> asynchronously and prevent the default browser form submission mechanism. See formium for details.

form.addEventListener('submit', gradual.hijack);

gradual.submit(options, done?)

This method can be used to submit an HTML <form> at will. You can also make AJAX submissions through gradual.submit with plain JavaScript object definitions, but still get the conventions.

Using <form> elements

In this case, the form submission will be identical as the form submissions hijacked by gradual.hijack.

gradual.submit({ form: form }, done);

Using plain objects

This use case is very similar to using a raw taunus.xhr call, except that you'll get the conventions from gradual. Events will be fired, and the response will be handled just like with gradual.hijack.

gradual.submit({
  method: 'POST',
  action: '/foo',
  data: {
    bar: 'baz'
  }
}, done);

Note that data will be passed directly to formulario, meaning you could easily set data to a <form> but submit it to an endpoint of your choosing.

gradual.transform(fn)

This method allows you to register a fn(form) callback that gets called whenever a form is submitted. You can prepare the form for submission in any way you want. You can optionally return a callback that restores the form to its original state.

The use case for gradual transforms is for those cases when you have a UX enhancement that breaks the state of the form, say if you were using insignia. In those cases, you can turn the field's value into something plain, and restore the more complex insignia tag editor right afterwards.

gradual.transform(function fix (form) {
  $(form).find('.nsg-input').forEach(function (input) {
    input.attr('data-prev', input.value());
    input.value(insignia(input).value());
  });
  return function restore () {
    $(form).find('.nsg-input').forEach(function (input) {
      input.value(input.attr('data-prev'));
    });
  };
});

Events

Whenever a response includes a Taunus redirect command (e.g the server-side response ended in a taunus.redirect call), or otherwise returns a form validation payload, gradual will respond to that accordingly.

Gradual always emits two of three events whenever a <form> submission gets its results back.

• error is emitted with (err) if there was an error generating or processing the response
• data is emitted with (data) if the response was successfully generated and processed
• response is always emitted with (err, data)

Custom Validation

Taunus'es gradual defines a flexible validation format where special responses will be captured and handled by gradual. Taunus looks for validation messages in all of the following fields JSON responses.

• validation
• messages
• model.validation
• model.messages
• flash.validation
• flash.messages
• flash.model.validation
• flash.model.messages

The validation model must be a non-empty array or any truthy value. If a validation model is found, a partials/form-validation partial view will be passed the validation model and rendered using Taunus.

License

MIT