how do i make a $.get request using coffeescript?

How do I do the following in CoffeeScript?

  $( function() {
    $('input#username').keyup( function() {
      var username = $('input#username').val();
      url = '/users/check_username/';
      params = { userna开发者_开发百科me : username };
      $.get(url, params, function(response){ markUsername(response); }, "json");
    });
  })

Here's another slightly condensed way to write it:

$ ->
  $('input#username').keyup ->
    username = $(this).val()
    callback = (response) -> markerUsername response
    $.get '/users/check_username/', {username}, callback, 'json'

Note the lack of parens, and the shorthand "{username}" object literal.

This is the best generic pattern I've come up with so far:

$.ajax '/yourUrlHere',
  data :
    key : 'value'
  success  : (res, status, xhr) ->
  error    : (xhr, status, err) ->
  complete : (xhr, status) ->

It compiles down to:

$.ajax('/yourUrlHere', {
  data: {
    key: 'value'
  },
  success: function(res, status, xhr) {},
  error: function(xhr, status, err) {},
  complete: function(xhr, status) {}
});

This is a way:

$(->
    $('input#username').keyup(->
        username = $('input#username').val()
        url = '/users/check_username/'
        params = {username: username}
        $.get(url, params, (response)->
            markerUsername(response)
        , "json")
    )
)

Some of these parenthesis can be omitted, but in my opinion, they help with understanding the code flow (at least in this situation).

I recommend fiddling around with coffeescript here http://jashkenas.github.com/coffee-script/ (use the "try coffeescript") button. The language is very easy to learn.