[Deno] Example for List subjects for a specific stream

examples/jetstream/list-subjects/deno/main.js

@@ -0,0 +1,92 @@
+import {
+    connect,
+    nuid
+} from "https://deno.land/x/[email protected]/src/mod.ts";
+
+const servers = Deno.env.get("NATS_URL")?.split(",");
+
+const nc = await connect({ servers });
+
+const jsm = await nc.jetstreamManager();
+const js = nc.jetstream();
+
+// Create a stream with a few random subjects
+const plainSubj = `PLAIN_${nuid.next().substring(18)}`;
+const gtSubj = `GT_${nuid.next().substring(18)}`;
+const starSubj = `STAR_${nuid.next().substring(18)}`;
+const name = `EVENTS_${nuid.next().substring(18)}`;
+
+let si = await jsm.streams.add({
+    name,
+    subjects: [plainSubj, `${gtSubj}.>`, `${starSubj}.*`]
+});
+
+console.log(`Stream: ${si.config.name} has these subjects: '${si.config.subjects}'`)
+
+// ### Get stream info with StreamInfoRequestOptions
+// Get the subjects via the streams.info call.
+// Since this is "state" there are no subjects in the state unless
+// there are messages in the subject.
+si = await jsm.streams.info(name, {subjects_filter: ">"});
+
+const count = si.state.subjects
+    ? Object.getOwnPropertyNames(si.state.subjects).length
+    : 0;
+console.log(`Before publishing any messages, there should be 0 subjects in the state: ${count}`)
+
+// console.log(`Before publishing any messages, there are 0 subjects: ${si.state.num_subjects}`)
+
+// Publish a message
+await js.publish(plainSubj)
+
+si = await jsm.streams.info(name, {subjects_filter: ">"});
+console.log("After publishing a message to a subject, it appears in state:")
+
+if (si.state.subjects) {
+    for (const [key, value] of Object.entries(si.state.subjects)) {
+        console.log(`  subject '${key}' has ${value} message(s)`)
+    }
+}
+
+// Publish some more messages, this time against wildcard subjects
+await js.publish(`${gtSubj}.A`, "gtA-1");
+await js.publish(`${gtSubj}.A`, "gtA-2");
+await js.publish(`${gtSubj}.A.B`, "gtAB-1");
+await js.publish(`${gtSubj}.A.B`, "gtAB-2");
+await js.publish(`${gtSubj}.A.B.C`, "gtABC");
+await js.publish(`${gtSubj}.B.B.B`, "gtBBB");
+await js.publish(`${starSubj}.1`, "star1-1");
+await js.publish(`${starSubj}.1`, "star1-2");
+await js.publish(`${starSubj}.2`, "star2");
+
+// Get all subjects
+si = await jsm.streams.info(name, {subjects_filter: ">"});
+console.log("Wildcard subjects show the actual subject, not the template.");
+
+if (si.state.subjects) {
+    for (const [key, value] of Object.entries(si.state.subjects)) {
+        console.log(`  subject '${key}' has ${value} message(s)`)
+    }
+}
+
+// ### Subject Filtering
+// Instead of allSubjects, you can filter for a specific subject
+si = await jsm.streams.info(name, {subjects_filter: `${gtSubj}.>`});
+console.log(`Filtering the subject returns only matching entries ['${gtSubj}.>']`);
+
+if (si.state.subjects) {
+    for (const [key, value] of Object.entries(si.state.subjects)) {
+        console.log(`  subject '${key}' has ${value} message(s)`)
+    }
+}
+
+si = await jsm.streams.info(name, {subjects_filter: `${gtSubj}.A.>`});
+console.log(`Filtering the subject returns only matching entries ['${gtSubj}.A>']`);
+
+if (si.state.subjects) {
+    for (const [key, value] of Object.entries(si.state.subjects)) {
+        console.log(`  subject '${key}' has ${value} message(s)`)
+    }
+}
+
+await nc.close();