ross-nordstrom · December 31, 2016 18:57 · Dec 31, 2016 · Dec 31, 2016
diff --git a/rxjs-recursive-poll.js b/rxjs-recursive-poll.js
@@ -0,0 +1,53 @@
+const rxjs = require('rxjs');
+
+/**
+ * The entrypoint function. Pass it the thing to call
+ */
+function dynamicPoll(pollFunc/*, delayFunc*/) {
+    // A recursive stream, which triggers   an API call
+    let i = 0; // just here for debugging
+    const trigger = new rxjs.BehaviorSubject(i++);
+
+    // The polling observable.
+    // While subscribed-to, it will continually call the "API", then queue up the next call
+    // Simple extensions:
+    //  - Delay the recursive API call (perhaps dynamic delay based on the previous call's latency)
+    //  - Use closure state to implement incremental queries (e.g. maintain and use a 'modifiedSince' option)
+    return trigger.concatMap(() => pollFunc(/*query, options*/)).map(res => {
+        trigger.next(i++); // RECURSE!
+        return res;
+    });
+}
+
+/**
+ * Mock API call
+ * Uses a delay to emulate an API with variable latency
+ * @return { time:string, delay:number, records:string[] }
+ */
+function fakeApi(/*query, options*/) {
+    const delay = random(250, 10*1000); // random delay between 250ms - 10s
+    const fakeRes = { time: shortDate(), delay: delay, records: ['fake api response'] };
+
+    return rxjs.Observable.of(fakeRes).delay(delay);
+}
+
+function random(min, max) {
+    return Math.round(Math.random() * (max - min) + min);
+}
+
+function shortDate() {
+    return new Date().toTimeString().slice(0,8); // e.g. "11:35:13"
+}
+
+function demo() {
+    console.warn('START DEMO');
+    let myDemo = dynamicPoll(fakeApi).subscribe(res => console.info('API Res: ' + JSON.stringify(res)));
+
+    setTimeout(() => {
+        myDemo.unsubscribe();
+        console.warn('END DEMO');
+    }, 60*1000);
+}
+
+// TO RUN, SIMPLY:
+// demo();