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    <p>There are a few problems with your code besides just the callback structure.</p> <pre><code>var contacts = req.body; (function(res, contacts) { ... })(); // function </code></pre> <p>^ you are redefining <code>contacts</code> and <code>res</code> in the parameter list, but not passing in any arguments, so inside your function <code>res</code> and <code>contacts</code> will be <code>undefined</code>.</p> <p>Also, not sure where your <code>self</code> variable is coming from, but maybe you defined that elsewhere.</p> <p>As to the callback structure, you're looking for something like this (assuming contacts is an Array):</p> <pre><code>exports.contacts_create = function(req, res) { var contacts = req.body; var iterator = function (i) { if (i &gt;= contacts.length) { res.json('finished'); // or call self.response() or whatever return; } contact = contacts[i]; var newContact = new Contact(contact); newContact.user = req.user.id newContact.save(function(err) { if (err) console.log(err); //if this is really a failure, you should call response here and return iterator(i + 1); //re-call this function with the next index }); }; iterator(0); //start the async "for" loop }; </code></pre> <p>However, you may want to consider performing your database saves in parallel. Something like this:</p> <pre><code>var savesPending = contacts.length; var saveCallback = function (i, err) { if (err) console.log('Saving contact ' + i + ' failed.'); if (--savesPending === 0) res.json('finished'); }; for (var i in contacts) { ... newContact.save(saveCallback.bind(null, i)); } </code></pre> <p>This way you don't have to wait for each save to complete before starting the next round-trip to the database.</p> <p>If you're unfamiliar with why I used <code>saveCallback.bind(null, i)</code>, it's basically so the callback can know which contact failed in the event of an error. See <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind" rel="nofollow">Function.prototype.bind</a> if you need a reference.</p>
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    1. USBret Copeland
    1. USBret Copeland
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    1. COI'd recommend using some async flow control module to handle async for loop. [caolan/async](https://github.com/caolan/async) is the easiest one to start with.
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      1. USLeonid Beschastny
    2. CO@LeonidBeschastny I try not to answer questions like this with just "use a library" since I think doing it yourself a few times helps new people understand the asynchronous concepts, and gives them the tools to do much more. However, using a library like async, and specifically `async.each()` in this case, would be a great idea in the long run.
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