Value from client.get() is "true" instead of the real value

Use Async Redis

npm i async-redis --save

const asyncRedis = require("async-redis");    
const client = asyncRedis.createClient(); 

await client.set("string key", "string val");
const value = await client.get("string key");

console.log(value);

await client.flushall("string key");

You are trying to use an async library in a sync way. This is the right way:

//REDIS
var redis = require("redis"),
    client = redis.createClient();

client.on("error", function (err) {
    console.log("Error "+ err);
});

client.set("card", "apple", function(err) {
    if (err) throw err;
});

everyone.now.signalShowRedisCard = function() {
    var self = this;
    client.get("card", function (err, res) {
        nowjs.getGroup(self.now.room).now.receiveShowRedisCard(res);
    });
}

You can also use a function provided by node_redis library
const getAsync = promisify(client.get).bind(client);
and use this to get values from redis as follows
const value = await getAsync(key)

One option is to use Bluebird to turn Redis callbacks into promises. Then you can use it with .then() or async/await.

import redis from 'redis'
import bluebird from 'bluebird'

bluebird.promisifyAll(redis)
const client = redis.createClient()

await client.set("myKey", "my value")
const value = await client.getAsync("myKey")

Notice your methods should have Async appened to them.