Change

<div id="diagram"></div>
<script>
  function onChange(e){
/* The result can be observed in the DevTools(F12) console of the browser. */
    console.log("Added items: " + e.added.length + "; Removed items: " + e.removed.length);
  }

  $("#diagram").kendoDiagram({
    shapes:[
      {
        id:"1",
        content:{
          text: "State 1"
        },
        x: 20,
        y: 20
      },
      {
        id:"2",
        content: {
          text: "State 2"
        },
        x: 160,
        y: 20
      }
    ],
    connections:[
      {
        from: "1",
        to: "2"
      }
    ],
    change: onChange
  });
</script>