async.series: variable number of callbacks

Question

I'm working in Node.js (Express) and MongoDB (mongooseJS). I want to create async functions (one after another, quering DB in proper order);

the question is: how can I create variable number of async.series functions, like this:

var supply = [0];
async.series([
      function(callback) {
        Model.find({ color: user.color[supply] }).exec(callback);
      },
  ],function(err, results){
    res.send('Chosen colors: ' + results);
});

and if - lets say - variable supply = [0, 1, 2],

then callback function will be tripled with 0, 1 and 2 placed there:

var supply = [0, 1, 2];
async.series([
      function(callback) {
        Model.find({ color: user.color[supply] }).exec(callback); // supply = 0
      },
      function(callback) {
        Model.find({ color: user.color[supply] }).exec(callback); // supply = 1
      },
      function(callback) {
        Model.find({ color: user.color[supply] }).exec(callback); // supply = 2
      },
  ],function(err, results){
    res.send('Chosen colors: ' + results);
});

in other words, how can i loop this fragment

      function(callback) {
        Model.find({ color: user.color[supply] }).exec(callback);
      },

so number of functions will be here depending on some variable?

Cheers!

Mike

mscdex · Accepted Answer · 2014-09-17 13:21:58Z

3

You could just use async.mapSeries() since it is designed to iterate over an array. Example:

var supply = [0];
async.mapSeries(supply, function(val, callback) {
  Model.find({ color: user.color[val] }).exec(callback);
}, function(err, results) {
  if (err) throw err;
  // all done!
  console.dir(results);
});

This assumes that .exec() calls the callback such that the error is first and the value is second.

answered Sep 17, 2014 at 13:21

mscdex

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