fix(cb-component-comm): check for isFirstChange (#3073)

* fix(cb-component-comm): check for isFirstChange

* update initial message

public/docs/_examples/cb-component-communication/e2e-spec.ts

@@ -65,7 +65,7 @@ describe('Component Communication Cookbook Tests', function () {
       let actual = getActual();
 
       let initialLabel = 'Version 1.23';
-      let initialLog = 'major changed from {} to 1, minor changed from {} to 23';
+      let initialLog = 'Initial value of major set to 1, Initial value of minor set to 23';
 
       expect(actual.label).toBe(initialLabel);
       expect(actual.count).toBe(1);

public/docs/_examples/cb-component-communication/ts/app/version-child.component.ts

@@ -21,10 +21,14 @@ export class VersionChildComponent implements OnChanges {
     let log: string[] = [];
     for (let propName in changes) {
       let changedProp = changes[propName];
-      let from = JSON.stringify(changedProp.previousValue);
       let to = JSON.stringify(changedProp.currentValue);
+      if (changedProp.isFirstChange()) {
+        log.push(`Initial value of ${propName} set to ${to}`);
+      } else {
+        let from = JSON.stringify(changedProp.previousValue);
         log.push(`${propName} changed from ${from} to ${to}`);
       }
+    }
     this.changeLog.push(log.join(', '));
   }
 }