How to return from async loops in Node.js

Question

When using async library for flow control, specifically async.forEach how do you properly perform a callback in case when you need to skip a specific item.

Example:

async.forEach(bigCollection, function(item, callback) {

    if(skipThis) {
        return callback();
        // OR BELLOW IS BETTER??
        //return process.nextTick(callback);
    }

    db.query(query, callback);

}, callback);

In case that I don't use process.nextTick(callback) do I risk running into stack overflow if the bigCollection is too big? And in case that I do use process.nextTick(callback) do I anyhow sabotage my code?

I have got into habit of doing it the process.nextTick(callback) way, however I am not so sure it's a good practice to do so.

Stack overflow? Why would you run into that? I don't see a reason why first solution would cause that and second not. On the other hand if your collection is really big, then stop thinking about semi-solutions and just partition it into smaller pieces and process piece by piece (you can for example wrap everything into async.series and run async.forEach in every piece). — freakish
– freakish, Commented Jul 19, 2012 at 11:19

Charles · Accepted Answer · 2012-07-19 11:20:25Z

2

I would say that without nextTick it's ok.

async.forEach(bigCollection, function(item, callback) {
    if(skipThis) {
        return callback();
    }
    db.query(query, callback);
}, callback);

If bigCollection is too big, then you will get the overflow before you come into the loop.

answered Jul 19, 2012 at 11:20

Charles

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