iframe-fileupload binding handler for knockout

gistfile1.coffee

ko.bindingHandlers.fileupload =
  init: (element, valueAccessor, allBindingsAccessor, viewModel, bindingContext) ->
    el = $(element).find('input')
    el.on 'change', (e) =>

      form = $('<form class="file-upload" target="_iframe" method="post" action="TARGET_URL" enctype="multipart/form-data"></form>')
      frame = $('<iframe name="_iframe">')

      frame.appendTo el.parent()
      el.wrap form
      frame.load ->
        frame.off 'load'
        err = null
        try
          data = $.parseJSON(frame.contents().text())
        catch e
          err = e
        el.unwrap()
        form.remove()
        frame.remove()
        valueAccessor().apply(viewModel, [err, data])

      el.parent().on('submit', (e) -> 
        e.stopPropagation()
      ).submit()