Adds Bloom Filter example using RedisBloom. (#1835)

* Adds Bloom Filter example using RedisBloom.

* Update bloom-filter.js

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

examples/bloom-filter.js

@@ -0,0 +1,79 @@
+// This example demonstrates the use of the Bloom Filter 
+// in the RedisBloom module (https://redisbloom.io/)
+
+import { createClient } from 'redis';
+
+async function bloomFilter() {
+  const client = createClient();
+
+  await client.connect();
+
+  // Delete any pre-existing Bloom Filter.
+  await client.del('mybloom');
+
+  // Reserve a Bloom Filter with configurable error rate and capacity.
+  // https://oss.redis.com/redisbloom/Bloom_Commands/#bfreserve
+  try {
+    await client.bf.reserve('mybloom', 0.01, 1000);
+    console.log('Reserved Bloom Filter.');
+  } catch (e) {
+    if (e.message.endsWith('item exists')) {
+      console.log('Bloom Filter already reserved.');
+    } else {
+      console.log('Error, maybe RedisBloom is not installed?:');
+      console.log(e);
+    }
+  }
+
+  // Add items to Bloom Filter individually with BF.ADD command.
+  await Promise.all([
+    client.bf.add('mybloom', 'leibale'),
+    client.bf.add('mybloom', 'simon'),
+    client.bf.add('mybloom', 'guy'),
+    client.bf.add('mybloom', 'suze'),
+    client.bf.add('mybloom', 'brian'),
+    client.bf.add('mybloom', 'steve'),
+    client.bf.add('mybloom', 'kyle'),
+    client.bf.add('mybloom', 'josefin'),
+    client.bf.add('mybloom', 'alex'),
+    client.bf.add('mybloom', 'nava'),
+  ]);
+
+  // Add multiple items to Bloom Filter at once with BF.MADD command.
+  await client.bf.mAdd('mybloom', [
+    'kaitlyn', 
+    'rachel'
+  ]);
+
+  console.log('Added members to Bloom Filter.');
+
+  // Check whether a member exists with the BF.EXISTS command.
+  const simonExists = await client.bf.exists('mybloom', 'simon');
+  console.log(`simon ${simonExists ? 'may' : 'does not'} exist in the Bloom Filter.`);
+
+  // Check whether multiple members exist with the BF.MEXISTS command:
+  const [ lanceExists, leibaleExists ] = await client.bf.mExists('mybloom', [
+    'lance',
+    'leibale'
+  ]);
+
+  console.log(`lance ${lanceExists ? 'may' : 'does not'} exist in the Bloom Filter.`);
+  console.log(`leibale ${leibaleExists ? 'may' : 'does not'} exist in the Bloom Filter.`);
+
+  // Get stats for the Bloom Filter with the BF.INFO command:
+  const info = await client.bf.info('mybloom');
+  // info looks like this:
+  //
+  //  {
+  //    capacity: 1000,
+  //    size: 1531,
+  //    numberOfFilters: 1,
+  //    numberOfInsertedItems: 12,
+  //    expansionRate: 2
+  //  }
+  console.log(info);
+
+  await client.quit();
+}
+
+bloomFilter();