Called when panels are being resized by the user. You can add event listener during the object creation: let layout = new w2layout({ name : 'layout', panels : [ { type: 'top', size: 40 }, { type: 'preview', size: 200 } ], onResizing: function(event) { console.log('panels of object '+ this.name + ' are being resized'); } }); or after the object has been created: w2ui.layout.on('resizing', function(event) { console.log('panels of object '+ this.name + ' are being resized'); }); You can add a listener to a panel, see .panels property. The event handler is called before the default action of the event is triggered. You can cancel the default action by calling event.preventDefault(). To perform an action after the event is fully processed, define event.onComplete function. See events page in utilities for more details.