Additional style for the .box where the object is rendered. You need to call .render() method to re-render the object if you changed this property during run-time. The .style property can be set during object creation. let layout = new w2layout({ name : 'layout', style : 'border: 1px solid red', panels : [ { type: 'top', size: 40 }, { type: 'preview', size: 200 } ] }); It is not recommended to change it during run-time as it requires complete re-render.