Step 15.14: Add a new response counting pipe

client/imports/app/shared/rsvp.pipe.ts

@@ -0,0 +1,22 @@
+import {Pipe, PipeTransform} from '@angular/core';
+import {Party} from "../../../../both/models/party.model";
+import {Parties} from "../../../../both/collections/parties.collection";
+
+@Pipe({
+  name: 'rsvp'
+})
+export class RsvpPipe implements PipeTransform {
+  transform(party: Party, type: string): number {
+    if (!type) {
+      return 0;
+    }
+
+    let total = 0;
+    const found = Parties.findOne(party._id);
+
+    if (found)
+      total = found.rsvps ? found.rsvps.filter(rsvp => rsvp.response === type).length : 0;
+
+    return total;
+  }
+}