In my projects I essentially found useful two ways to encrypt strings: hash functions one-way and one-way and encryption-decryption two-way :

1. Hash functions with Bcrypt

Hash functions are essentials for store encrypted password, and the best library for nodejs is Bcrypt. You can find more information in this article: why use Bcrypt?.

Install:

npm install bcrypt

To hash a password:

const bcrypt = require('bcrypt');
const saltRounds = 10;
const myPlaintextPassword = 'myPassword';

bcrypt.hash(myPlaintextPassword, saltRounds).then(function(hash) {
	// Store hash in your password DB.
});

At user login to compare password with the one stored in the db you can use:

bcrypt.compare(plaintextPassToCheck, hashStoredInDB).then(function(res) {
  // res == true/false
});

More info: github.com/kelektiv/node.bcrypt.js

2. Simple Encryption and Decryption

In other scenarios I needed to crypt strings in order to hide texts to users but in a way that permits me to decrypt and retrieve the original content. In this case a fast tool is Crypto.

Install:

npm install crypto

To encrypt and decrypt a string:

var crypto = require('crypto');

var cypherKey = "mySecretKey";

function encrypt(text){
  var cipher = crypto.createCipher('aes-256-cbc', cypherKey)
  var crypted = cipher.update(text,'utf8','hex')
  crypted += cipher.final('hex');
  return crypted; //94grt976c099df25794bf9ccb85bea72
}

function decrypt(text){
  var decipher = crypto.createDecipher('aes-256-cbc',cypherKey)
  var dec = decipher.update(text,'hex','utf8')
  dec += decipher.final('utf8');
  return dec; //myPlainText
}

More info: nodejs.org/api/crypto