How to use Redis from Node.js

One of the most popular libraries to work with a Redis server from a Node.js app is node-redis, available at https://github.com/NodeRedis/node-redis.

Install the library in your project:

npm install redis

Tip: don’t forget to first run npm init -y if the project is brand new and you don’t have a package.json file already.

Connect to the Redis instance

Once the library is installed, require it in your project using

const redis = require('redis')

or

import redis from 'redis'

Once you have the redis object, create a new client using

const client = redis.createClient({
  url: 'redis://YOUR REDIS INSTANCE URL'
})

and connect using (inside an async function):

await client.connect()

Once you have the client, we can perform all the things we know that Redis can do.

To close the connection, call:

client.quit()

Store and retrieve key values

Store a key value pair into redis using set():

client.set("<key>", "<value>")

Example:

client.set("name", "Flavio")
client.set("age", 37)

If you run KEYS * in redis-cli on a clean Redis server, you’ll see the two keys appearing:

You can get the value stored in a key using get():

const value = await client.get("name")

Delete a key/value string using

client.del("names")

Working with lists

In Redis we can work with lists using the

• LPUSH
• RPUSH
• LTRIM
• LRANGE

commands we introduced in the Redis module. They map directly as client object methods.

Create a list using

client.lPush('names', 'Flavio')

Push a new item to the bottom of the list:

client.rPush('names', 'Roger')

Or at the top of the list:

client.lPush('names', 'Syd')

List all the items in a list using:

const result = await client.lRange('names', 0, -1)
//result is [ 'Roger', 'Flavio', 'Syd' ]

Drop items from a list using

client.rPop('names')

Delete a list using

client.del('names')

Working with sets

In Redis we work with sets using

• SADD
• SPOP
• SMEMBERS.

and other Redis commands, that map directly as client object methods.

Create a set using

client.sAdd('names', 'Flavio')

Add more items to the set:

client.sAdd('names', 'Roger')

You can add multiple ones at once:

client.sAdd('names', 'Roger', 'Syd')

also by passing an array:

const names = ['Flavio', 'Roger', 'Syd']
client.sAdd('names', names)

List all the items in a set using:

const names = await client.sMembers('names')

Drop a random item from a set using:

client.sPop('names')

Add a second parameter to drop multiple random items:

client.sPop('names', 3)

Delete a set using

client.del('names')

Working with hashes

In Redis we work with hashes using a set of commands that include

• HMSET
• HGETALL
• HSET
• HINCRBY.

and other commands we introduced in the Redis module, that map directly as client object methods.

Create a hash using

client.hSet('person:1', 'name', 'Flavio', 'age', 37)

To get all the properties of a user, use HGETALL:

const items = client.hGetAll('person:1')

You can update a hash property using HSET:

client.hSet('person:1', 'age', 38)

You can increment a value stored in a hash using HINCRBY:

client.hIncrBy('person:1', 'age', 1)

Delete a hash using

client.del('person:1')

Subscriptions

Subscriptions are an amazing feature of Redis, powering us to do really fancy things in Node.js.

A publisher sends a message on a channel. Multiple subscribers receive it.

Subscribe to a channel using

await subscriber.subscribe('dogs', (message) => {
  console.log(message);
})

Publish to a channel using client.publish('<channel>', '<message>')

client.publish('dogs', 'Roger')

Be aware that you can’t publish and subscribe from the same client instance.

To do so in the same app, create 2 clients:

const subscriber = redis.createClient({ ... })
const publisher = redis.createClient({ ... })

await subscriber.subscribe('dogs', (message) => {
  console.log(channel, message);
})

publisher.publish('dogs', 'Roger')