gistfile1.js

App.NavPanelView = Ember.View.extend({
  closedHeight: 40,
  openedHeight: 500,

  mouseover: function(){
    var openedHeight = this.get('openedHeight');
    this.$().animate({ height: openedHeight }, 'fast');
  },

  mouseout: function(){
    var closedHeight = this.get('closedHeight');
    this.$().animate({ height: closedHeight }, 'fast');
  }
});