Adds example of using a trim strategy with XADD. (#2105)

* Adds example of using a trim strategy with XADD.

* Update stream-producer.js

Co-authored-by: Leibale Eidelman <leibale1998@gmail.com>

examples/stream-producer.js

@@ -1,5 +1,4 @@
 // A sample stream producer using XADD.
-
 import { createClient } from 'redis';
 
 async function streamProducer() {
@@ -7,18 +6,45 @@ async function streamProducer() {
 
   await client.connect();
   
-  let num = 0;
+  for (let i = 0; i < 10000; i++) {
-
+    await client.xAdd(
-  while (num < 1000) {
+      'mystream',
-    // * = Let Redis generate a timestamp ID for this new entry.
+      '*', // * = Let Redis generate a timestamp ID for this new entry.
-    let id = await client.xAdd('mystream', '*', {
+      // Payload to add to the stream:
-      num: `${num}`
+      {
+        i: i.toString()
         // Other name/value pairs can go here as required...
-    });
-
-    console.log(`Added ${id} to the stream.`);
-    num += 1;
       }
+    );
+
+    // Also add to a stream whose length we will cap at approximately
+    // 1000 entries using the MAXLEN trimming strategy:
+    // https://redis.io/commands/xadd/
+
+    await client.xAdd(
+      'mytrimmedstream', 
+      id, // Re-use the ID from the previous stream.
+      // Payload to add to the stream:
+      {
+        i: i.toString()
+        // Other name/value pairs can go here as required...
+      },
+      // Specify a trimming strategy...
+      {
+        TRIM: {
+          strategy: 'MAXLEN', // Trim by length.
+          strategyModifier: '~', // Approximate trimming.
+          threshold: 1000 // Retain around 1000 entries.
+        }
+      }
+    );
+  }
+
+  // Take a look at how many entries are in the streams...
+  // Should be 10000:
+  console.log(`Length of mystream: ${await client.xLen('mystream')}.`);
+  // Should be approximately 1000:
+  console.log(`Length of mytrimmedstream: ${await client.xLen('mytrimmedstream')}.`);
 
   await client.quit();
 }