node.js async each function callback failing

Question

I'm making a call to my db, and want to use the results to fire off a request to another server, and then handle the responses. I want to do this asynchronously so I am trying to use the async library.

var sendRequest = function (store) {

    console.log(store);
}

connection.connect();

connection.query('SELECT * from stores', function(err, rows, fields) {
    if (!err){
        async.each(rows, function(row, sendRequest) {
            var store = {id: row.id, address: row.address};
            //console.log(store); <-- this works
            sendRequest(store); <-- this logs {id: '', address: null} only once
        }, function(err){
            console.log(err);
        });
    }
    else
        console.log('Error performing query');
});

connection.end();

If I log the store variable directly, it logs for each instance in the array rows and properly. If I try to do it through the sendRequest callback, it does it only once and improperly.

Can you tell me if you are using the nodeJS "async" library here? npmjs.com/package/async#each — Norman Breau
– Norman Breau, Commented Apr 29, 2015 at 2:10
It's probably a bad idea to have two variables named sendRequest. It can cause potential confusion making people think the sendRequest inside the async.each callback have anything to do with the sendRequest function at the top. — slebetman
– slebetman, Commented Apr 29, 2015 at 2:16
@haaduken: Ha! see! even you are confused! Then rename the other variable (the function argument) to something else to stop it from being overridden. — slebetman
– slebetman, Commented Apr 29, 2015 at 2:21

Rodrigo Medeiros · Accepted Answer · 2015-04-29 02:20:17Z

2

You confused some things. You're using the same name, sendRequest, for the each callback. You should do instead:

connection.query('SELECT * from stores', function(err, rows, fields) {
  if (!err){
    async.each(rows, function(row, callback) {
        var store = {id: row.id, address: row.address};
        sendRequest(store);
        callback();

    }, function(err){
        console.log(err);
    });
  }
  else
    console.log('Error performing query');
});

answered Apr 29, 2015 at 2:20

Rodrigo Medeiros

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3 Comments

haaduken Over a year ago

so what goes in callback and where is it defined?

slebetman Over a year ago

@haaduken: That callback is passed to you by async.each, just like row

Rodrigo Medeiros Over a year ago

callback is an argument of the function that async.each has to call for each item in the array, to notify that it has finished. You can use whatever name you want, just make sure that this name is not in use by other functions or variables.

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