ColumnResizing Property (ColumnResizingClientEvents)

// The client event ColumnResizing takes two parameters sender and e
// sender  is the object which is raising the event
// e is the ColumnResizingEventArgs

 function WDG1_ColumnResizing(sender, e) {
    
     //Returns which column is being used as the drag source for the resize action
     var column = e.get_column();

     //Gets the key of the column
     var key = column.get_key();

     if (!confirm("Are you sure you want to change the width of the column '" + key + "' ?"))
        
        //Cancels the 'ColumnResizing' event
         e.set_cancel(true);  

 }