This is an extension to Chosen, which dynamically creates an option element as you type. It's useful when you want to provide a user with several predefined options, but want to also give them the option to add their own, without needing another input field.
Note: This currently only supports jQuery. Let me know if you'd like prototype support, or feel free to submit a pull request!
$('.my-select').chosen().chosenDynamic({
debounce: 500
});
$.chosenDynamic(options:Object)
{
// how long to wait before updating the select, default is 500
debounce: 500
}