Asynchronously get generated array on function and pass it out of the box

Question

Problem resolved on Asynchronously solution to check data from database kinds of loop clause

with this below code i can generate simple array as jsonArray into checkUserMobileNumberAsEwallet function, but i can't pass it out of that to send inside client,

with socket.emit('syncContacts', accountNumbers) i get [] result on accountNumbers, but into if (success) { statement array successful created and pushed into accountNumbers array

socket.on('syncContacts', function (data) {
    var accountNumbers = [];

    for (var i = 0; i < data.length; i++) {
        checkUserMobileNumberAsEwallet(data[i].mobileNumber, function (success) {
            if (success) {
                accountNumbers.push({ewalletNumber: this.mobileNumber});
                console.log(accountNumbers);
            }
        }.bind({mobileNumber: data[i].mobileNumber}));
    }
    console.log(accountNumbers);

    socket.emit('syncContacts', accountNumbers);
});

function checkUserMobileNumberAsEwallet(mobileNumber, callback) {
    var mobileNumber = mobileNumber.substr(1, mobileNumber.length);

    var query = "SELECT id FROM userEwallets WHERE ewalletNumber LIKE '%" + mobileNumber + "'";
    connection.query(query, function (err, results) {
        if (err) return callback(false);

        if (results.length === 0)
            return callback(false);
        else {
            return callback(true);
        }

    });
}

Updated after post comments:

socket.on('syncContacts', function (data) {

    //console.log(accountNumbers);

    //socket.emit('syncContacts', accountNumbers);

    async.parallel(
        [
            function (callback) {
                var accountNumbers = [];

                for (var i = 0; i < data.length; i++) {
                    checkUserMobileNumberAsEwallet(data[i].mobileNumber, function (success) {
                        if (success) {
                            accountNumbers.push({ewalletNumber: this.mobileNumber});
                            console.log(accountNumbers);
                        }
                    }.bind({mobileNumber: data[i].mobileNumber}));
                }
                callback(success, accountNumbers);
            }
        ],
        function (success, results) {
            console.log("results " + results.toString());
            socket.emit('syncContacts', results);
        });
});

function checkUserMobileNumberAsEwallet(mobileNumber, callback) {
    var mobileNumber = mobileNumber.substr(1, mobileNumber.length);

    var query = "SELECT id FROM userEwallets WHERE ewalletNumber LIKE '%" + mobileNumber + "'";
    connection.query(query, function (err, results) {
        if (err) return callback(false);

        if (results.length === 0)
            return callback(false);
        else {
            return callback(true);
        }
    });
}

I'm not sure what socket library you're using, but perhaps the data sent with `.emit` should be a string? — Whothehellisthat, Aug 05 '16 at 16:52
@JoseRojas no, i dont get any error, code work fine, but when i push items to array i cant get that out of function — mahdi pishguy, Aug 05 '16 at 16:57
@Whothehellisthat problem is content of array which i get null to send — mahdi pishguy, Aug 05 '16 at 16:58
@mahdipishguy, your problem is that the `if (success)` block happens *asynchronously*. This leads to your `socket.emit` call happening before the `if (success)` block. You need to call `socket.emit` asynchronously as well. See Michael Camden's answer below. — dshapiro, Aug 05 '16 at 17:32

score 0 · Answer 1 · answered Aug 05 '16 at 16:54

Based on our code, it seems like checkUserMobileNumberAsEwallet is an asynchronous event, which accepts a function callback. That would mean that the for-loop would execute, which would queue up executions to checkUserMobileNumberAsEwallet. Immediately after the for-loop executes, console.log would correctly output the empty array accountNumbers and emit the event through the socket. Then the callback functions to each checkUserMobileNumberAsEwallet execution would begin to execute, and log the accountNumbers array which now has data.

This can be solved in a few ways, but likely the easiest and most readable would be to create Promises, and act on the Promises when they resolve. Personally I like the 'when' promise library, but many libraries could help to solve this problem. https://github.com/cujojs/when/blob/master/docs/api.md#whensettle

@Michael Camden on `if` statement i get `[ { ewalletNumber: '7892331743' } ]` and after finishing that such as `for` i get `[]` — mahdi pishguy, Aug 05 '16 at 17:01
@Michael Camden My post updated, could you review again? thanks — mahdi pishguy, Aug 05 '16 at 17:50

dshapiro · Answer 2 · 2016-08-05T17:52:12.113

0

The problem is that you have no control over when the code inside the callback executes, and it ends up executing after you've already called socket.emit.

You can either a) use an async aggregator to call a callback for each successful mobile number and then, when all of those have finished, call the socket.emit call OR b) do something like what I did below. Alter your checkUserMobileNumberAsEwallet function to accept and verify an array of mobile numbers, and pass the successful numbers to your callback function

Try the following:

socket.on('syncContacts', function (data) {
  var accountNumbers = [];
  var mobileNumbers = [];

  for (var i = 0; i < data.length; i++) {
    mobileNumbers.push(data[i].mobileNumber);
  }

  checkUserMobileNumberAsEwallet(mobileNumbers, function (successfulNumbers) {
      if (successfulNumbers.length > 0) {
          for (var i = 0; i < successfulNumbers.length; i++) {
              accountNumbers.push({ewalletNumber: successfulNumbers[i]});
          }
          socket.emit('syncContacts', accountNumbers);
      }
   }.bind({mobileNumbers: mobileNumbers}));
});

edited Aug 05 '16 at 17:52

answered Aug 05 '16 at 17:38

dshapiro

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i want to send created array not post that every for loop statement – mahdi pishguy Aug 05 '16 at 17:41
my post updated sir – mahdi pishguy Aug 05 '16 at 17:49
I see your update. I'm not sure how async.parallel works. Will it call the array of callbacks followed by the single callback with the socket.emit? If so, that sounds like what you want. – dshapiro Aug 05 '16 at 17:55
could you update my `checkUserMobileNumberAsEwallet` function? i cant get result, result for send is empty too – mahdi pishguy Aug 05 '16 at 18:09
Ha, someone just went through and downvoted the question and answers. What a cheeseball. – dshapiro Aug 05 '16 at 18:59
upvoted your post by me, i dont know went through and downvoted – mahdi pishguy Aug 06 '16 at 09:31

Asynchronously get generated array on function and pass it out of the box

Problem resolved on Asynchronously solution to check data from database kinds of loop clause

Updated after post comments:

2 Answers2

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