_sample.js

el.addEventListener('click', function openDialog(event) {
  // open the dialog
});

sample.coffee

el.addEventListener 'click', openDialog = (event) ->
  # open the dialog

# no thanks

sample.coffee.js

// what the coffeescript becomes
var openDialog;

el.addEventListener('click', openDialog = function(event) {
  // open the dialog
});

wouldBeCoolerIf.coffee.js

// what the coffeescript COULD become
// Using solution described here: http://kangax.github.com/nfe/#jscript-memory-management

// If the intention is to have a named-func-expression (just for debugging, not referenc'able by name):
el.addEventListener('click',
  (function(){
    var openDialog, f = function openDialog(event) {
      // open the dialog
    };
    openDialog = null; // null so that openDialog does not reference extraneous func
    return f;
  }())
);

// If the intention is to have the same BUT referenc'able by name:
var openDialog;
el.addEventListener('click',
  openDialog = (function(){
    var openDialog, f = function openDialog(event) {
      // open the dialog
    };
    openDialog = null; // null so that openDialog does not reference extraneous func
    return f;
  }())
);