#2287 Add example scripts showing pub/sub usage. (#2288)

* #2287 Add example scripts showing pub/sub usage.
redis/node-redis#2287

* #2287 Add example scripts showing pub/sub usage.
Fixing comments requested
Adding client.connect() to pubsub-subscriber.js
Reformatting Readme
updating logging in pubsub-publisher.js

* #2287 Add example scripts showing pub/sub usage.
Fix publish and subscriber
Update tidy up comments

* Update examples/pubsub-subscriber.js

Making suggested changes

Co-authored-by: Simon Prickett <simon@crudworks.org>

Co-authored-by: Simon Prickett <simon@crudworks.org>

Closes #2287.

examples/README.md

@@ -14,6 +14,8 @@ This folder contains example scripts showing how to use Node Redis in different
 | `hyperloglog.js`            | Showing use of Hyperloglog commands [PFADD, PFCOUNT and PFMERGE](https://redis.io/commands/?group=hyperloglog)                                |
 | `lua-multi-incr.js`         | Define a custom lua script that allows you to perform INCRBY on multiple keys                                                                       |
 | `managing-json.js`          | Store, retrieve and manipulate JSON data atomically with [RedisJSON](https://redisjson.io/)                                                         |
+| `pubsub-publisher.js`       | Adds multiple messages on 2 different channels messages to Redis                                                                                    |
+| `pubsub-subscriber.js`      | Reads messages from channels using `PSUBSCRIBE` command                                                                                             |
 | `search-hashes.js`          | Uses [RediSearch](https://redisearch.io) to index and search data in hashes                                                                         |
 | `search-json.js`            | Uses [RediSearch](https://redisearch.io/) and [RedisJSON](https://redisjson.io/) to index and search JSON data                                      |
 | `set-scan.js`               | An example script that shows how to use the SSCAN iterator functionality                                                                            |

examples/pubsub-publisher.js

@@ -0,0 +1,20 @@
+// A sample publisher using the publish function to put message on different channels.
+// https://redis.io/commands/publish/
+import { createClient } from 'redis';
+
+const client = createClient();
+
+await client.connect();
+
+// Declare constant variables for the name of the clients we will publish to as they will be required for logging.
+const channel1 = 'chan1nel';
+const channel2 = 'chan2nel';
+
+for (let i = 0; i < 10000; i++) {
+  // 1st channel created to publish 10000 messages.
+  await client.publish(channel1, `channel1_message_${i}`);
+  console.log(`publishing message on ${channel1}`);
+  // 2nd channel created to publish 10000 messages.
+  await client.publish(channel2, `channel2_message_${i}`);
+  console.log(`publishing message on ${channel2}`);
+}

examples/pubsub-subscriber.js

@@ -0,0 +1,41 @@
+// A sample subscriber showing how the subscribe method and pSubscribe method work.
+// https://redis.io/commands/subscribe/
+// https://redis.io/commands/pSubscribe/
+// This consumes messages published by pubsub-publisher.js
+
+import { createClient} from 'redis';
+
+// Create and connect client before executing any Redis commands.
+const client = createClient();
+await client.connect();
+
+// Each subscriber needs to connect individually therefore we duplicate the client.
+const channel1Sub = client.duplicate();
+const channel2Sub = client.duplicate();
+const noChannelsSub = client.duplicate();
+const allChannelsSub = client.duplicate();
+
+await channel1Sub.connect();
+await channel2Sub.connect();
+await noChannelsSub.connect();
+await allChannelsSub.connect();
+
+// This subscriber only will receive messages from channel 1 as they are using the subscribe method and subscribed to chan1nel.
+await channel1Sub.subscribe('chan1nel', (message) => {
+  console.log(`Channel1 subscriber collected message: ${message}`);
+},true);
+
+// This subscriber only will receive messages from channel 2 as they are using the subscribe method and subscribed to chan2nel.
+await channel2Sub.subscribe('chan2nel', (message) => {
+  console.log(`Channel2 subscriber collected message: ${message}`);
+},true);
+
+// This subscriber will not receive any messages as its channel does not exist.
+await noChannelsSub.subscribe('chan*nel', (message) => {
+  console.log(`This message will never be seen as we are not using pSubscribe here. ${message}`);
+},true);
+
+// This subscriber receive messages from both channel 1 and channel 2 using the pSubscribe method.
+await allChannelsSub.pSubscribe('chan*nel', (message, channel) => {
+  console.log(`Channel ${channel} sent message: ${message}`);
+},true);