The following list contains events that you can react on:

• change - generic event triggered for any change in the graph
• add - triggered when a new cell is added to the graph
• remove - triggered when a cell is removed from the graph
• Moreover, all the events that are triggered on elements or links are propagated to the graph as well.

graph.on('add', function(cell) { 
    alert('New cell with id ' + cell.id + ' added to the graph.') 
})