Text box auto resize

autoresize.coffee

ko.bindingHandlers.autoResize =
  init: (element, _valueAccessor, allBindings) ->
    $(element).addClass("resizable")

    observable = allBindings().textInput
    updateHeight = (element) ->
      $(element).css("height", "1px")
      totalHeight = element.scrollHeight
      $(element).css("height", "#{totalHeight}px")

    if ko.isObservable(observable)
      observable.subscribe((newValue) ->
        updateHeight element
      )
    else
      $(element).on ("input"), (evt) ->
        updateHeight this