Fix callback.

src/operations/balanceChart.component.ts

@@ -147,7 +147,7 @@ export class BalanceChartComponent implements OnInit, OnChanges {
       },
       subchart: {
         show: true,
-        onbrush: function(domain) {
+        onbrush: (domain) => {
           this.onUpdate.emit({minDate: domain[0], maxDate: domain[1]});
         }
       }