Array is empty, no data after for loop added

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.

Does this answer your question? [Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference](https://stackoverflow.com/questions/23667086/why-is-my-variable-unaltered-after-i-modify-it-inside-of-a-function-asynchron) — CertainPerformance, Mar 14 '20 at 08:30
Indeed, it's not working because you're altering it in an asynchronous callback — CertainPerformance, Mar 14 '20 at 08:37
but how i can do that ? i tried a lot of example code but none working for this situation. — Thai BNM, Mar 14 '20 at 08:40
Look at the linked question and https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call. Put the functionality you need inside the callback — CertainPerformance, Mar 14 '20 at 08:41
Hey i just found out it's working now ... thank you very much! — Thai BNM, Mar 14 '20 at 08:42

score 0 · Answer 1 · answered Mar 14 '20 at 08:42

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(); 
       });
    }
});

score 0 · Answer 2 · answered Mar 14 '20 at 08:42

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();

Array is empty, no data after for loop added

2 Answers2