How to run a variable series or javascript functions in node.js using async?

Question

I'm using async with Node.js. It runs fine when I have a fixed number of functions to execute:

async.series([ 
    function(cb) { ...one ... },
    function(cb) { .. two ... },
], function(err, res) {
    ...done
});

But now I need to execute an arbitrary number of functions, depending on values in one array, and cannot figure how to pass the array elements:

var values = [1, 2, 3, ... ];
var calls = [];
for (var i = 0; i < values.length; i++) {
    calls.push(function(cb) { 

        HOW TO PASS values[i] HERE? 

    });
}
async.series(calls, function(err, res) {
    ...done
});

Bergi · Accepted Answer · 2012-09-14 11:10:56Z

2

That's just the common async-in-a-loop problem. You will need a closure for the value of i, in which the pushed function expression is declared. This can either be done with an IEFE as your loop body, or even easier with .forEach() or .map():

 var calls = values.map(function closure(val, i) {
     return function(cb) {
         // use val and i here, which are bound to this execution of closure
     };
 });

answered Sep 14, 2012 at 11:10

Bergi

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rbginge · Accepted Answer · 2012-09-14 11:10:14Z

1

You should be able to use a closure:

var values = [1, 2, 3, ... ];
var calls = [];
for (var i = 0; i < values.length; i++) {
    calls.push((function(index) {
        return function(cb) {       
            // use values[index] here
        };
    })(i));
}
async.series(calls, function(err, res) {
    ...done
});

answered Sep 14, 2012 at 11:10

rbginge

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