coffee script ex jquery+lowpro behavior

behavior.coffee

TextareaExpander = $.klass({
  contructor: (pixelsToGrowBy, maxHeight) ->
    @pixelsToGrowBy = pixelsToGrowBy ? 20
    @maxHeight = maxHeight ? 999
    this.onkeypress
    
  onkeypress: (event) ->
    currentHeight = this.element.height
    scrollHeight = this.element[0].scrollHeight
    while currentHeight < scrollHeight and currentHeight < @maxHeight
      this.element.css({'height': (currentHeight + @pixelsToGrowBy) + 'px'})
      currentHeight = this.element.height
      scrollHeight = this.element[0].scrollHeight
})

behavior.js

(function() {
  var TextareaExpander;
  TextareaExpander = $.klass({
    contructor: function(pixelsToGrowBy, maxHeight) {
      this.pixelsToGrowBy = pixelsToGrowBy != null ? pixelsToGrowBy : 20;
      this.maxHeight = maxHeight != null ? maxHeight : 999;
      return this.onkeypress;
    },
    onkeypress: function(event) {
      var currentHeight, scrollHeight, _results;
      currentHeight = this.element.height;
      scrollHeight = this.element[0].scrollHeight;
      _results = [];
      while (currentHeight < scrollHeight && currentHeight < this.maxHeight) {
        this.element.css({
          'height': (currentHeight + this.pixelsToGrowBy) + 'px'
        });
        currentHeight = this.element.height;
        _results.push(scrollHeight = this.element[0].scrollHeight);
      }
      return _results;
    }
  });
}).call(this);

orig.js

TextareaExpander = $.klass({
  initialize: function(pixelsToGrowBy, maxHeight) {
    this.pixelsToGrowBy = (typeof pixelsToGrowBy == 'undefined') ? 20 : pixelsToGrowBy;
    this.maxHeight = (typeof maxHeight == 'undefined') ? 999 : maxHeight;
    // run it once to blow up any textareas on first page load
    this.onkeypress();
  },

  onkeypress: function(e) {
    var curr_h = this.element.height();
    var scroll_h = this.element[0].scrollHeight;
    while(curr_h < scroll_h && curr_h < this.maxHeight) {
      this.element.css( { 'height': (curr_h + this.pixelsToGrowBy) + 'px' });
      curr_h = this.element.height();
      scroll_h = this.element[0].scrollHeight;
    }
  }
});