Array is empty, no data after for loop added - node.js

Question

I'm using redis and nodejs for the first time, without success. Trying to loop insert data but got an empty array.
const redis = require("redis");
const client = redis.createClient({
retry_strategy: function(options) {
if (options.error && options.error.code === "ECONNREFUSED") {
// End reconnecting on a specific error and flush all commands with
// a individual error
return new Error("The server refused the connection");
}
if (options.total_retry_time > 1000 * 60 * 60) {
// End reconnecting after a specific timeout and flush all commands
// with a individual error
return new Error("Retry time exhausted");
}
if (options.attempt > 10) {
// End reconnecting with built in error
return undefined;
}
// reconnect after
return Math.min(options.attempt * 100, 3000);
},
});
var data_value = {
id: '235235',
totalrv: 'WAIT',
product: 'productName2',
url: 'url2',
process: 'proc',
task: 'msg'
};
client.set("key0", JSON.stringify(data_value));
client.set("key1", JSON.stringify(data_value));
client.set("key2", JSON.stringify(data_value));
client.set("key3", JSON.stringify(data_value));
client.set("key4", JSON.stringify(data_value));
//client.get("key2", redis.print);
var logger_data = {
logger: []
};
client.keys('*', function (err, keys) {
if (err) return console.log(err);
for(var i = 0, len = keys.length; i < len; i++) {
var values_v = client.get(keys[i].toString(), function(err, val) {
// console.log(logger_data);
// data is exist ...
logger_data.logger.push(JSON.parse(val));
});
}
});
// empty data
console.log(logger_data);
I wrote 2 print data result, in the loop it's working ok, but end of function, there are no data in array.

Answer 1

you can call a function inside the callback if you want to print the logger_data with values outside the asynchronous callback, like this
function printLoggerData(){
console.log(logger_data);
}
client.keys('*', function (err, keys) {
if (err) return console.log(err);
for(var i = 0, len = keys.length; i < len; i++) {
var values_v = client.get(keys[i].toString(), function(err, val) {
// console.log(logger_data);
// data is exist ...
logger_data.logger.push(JSON.parse(val));
// calling the function here so that it contains the latest values
printLoggerData();
});
}
});

Answer 2

Ok, with help of CertainPerformance, it's now working in asynchronous.
Thank you very much ...
async function getMessage () {
var logger_data = {
logger: []
};
return new Promise(function(resolve, reject) {
client.keys('*', function (err, keys) {
if (err) return console.log(err);
for(var i = 0, len = keys.length; i < len; i++) {
var values_v = client.get(keys[i].toString(), function(err, val) {
logger_data.logger.push(JSON.parse(val));
resolve(logger_data);
});
}
});
});
}
async function main() {
let message = await getMessage();
console.log(message);
}
main();