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copied!<p><strong>Update:</strong></p> <p>Now I would advise to have a look at:</p> <ul> <li><p><strong><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" rel="noreferrer">Promises</a></strong> </p> <blockquote> <p>The Promise object is used for deferred and asynchronous computations. A Promise represents an operation that hasn't completed yet, but is expected in the future.</p> </blockquote> <p>A popular promises library is <a href="http://bluebirdjs.com/docs/getting-started.html" rel="noreferrer">bluebird</a>. A would advise to have a look at <a href="http://bluebirdjs.com/docs/why-promises.html" rel="noreferrer">why promises</a>.</p> <blockquote> <p>You should use promises to turn this:</p> <pre><code>fs.readFile("file.json", function (err, val) { if (err) { console.error("unable to read file"); } else { try { val = JSON.parse(val); console.log(val.success); } catch (e) { console.error("invalid json in file"); } } }); </code></pre> <p>Into this:</p> <pre><code>fs.readFileAsync("file.json").then(JSON.parse).then(function (val) { console.log(val.success); }) .catch(SyntaxError, function (e) { console.error("invalid json in file"); }) .catch(function (e) { console.error("unable to read file"); }); </code></pre> </blockquote></li> <li><p><strong>generators:</strong> For example via <a href="https://github.com/tj/co" rel="noreferrer">co</a>. </p> <blockquote> <p>Generator based control flow goodness for nodejs and the browser, using promises, letting you write non-blocking code in a nice-ish way.</p> <pre><code>var co = require('co'); co(function *(){ // yield any promise var result = yield Promise.resolve(true); }).catch(onerror); co(function *(){ // resolve multiple promises in parallel var a = Promise.resolve(1); var b = Promise.resolve(2); var c = Promise.resolve(3); var res = yield [a, b, c]; console.log(res); // => [1, 2, 3] }).catch(onerror); // errors can be try/catched co(function *(){ try { yield Promise.reject(new Error('boom')); } catch (err) { console.error(err.message); // "boom" } }).catch(onerror); function onerror(err) { // log any uncaught errors // co will not throw any errors you do not handle!!! // HANDLE ALL YOUR ERRORS!!! console.error(err.stack); } </code></pre> </blockquote></li> </ul> <hr> <p>If I understand correctly I think you should have a look at the very good <a href="https://github.com/caolan/async" rel="noreferrer">async</a> library. You should especially have a look at the <a href="https://github.com/caolan/async#series" rel="noreferrer">series</a>. Just a copy from the snippets from github page:</p> <pre><code>async.series([ function(callback){ // do some stuff ... callback(null, 'one'); }, function(callback){ // do some more stuff ... callback(null, 'two'); }, ], // optional callback function(err, results){ // results is now equal to ['one', 'two'] }); // an example using an object instead of an array async.series({ one: function(callback){ setTimeout(function(){ callback(null, 1); }, 200); }, two: function(callback){ setTimeout(function(){ callback(null, 2); }, 100); }, }, function(err, results) { // results is now equals to: {one: 1, two: 2} }); </code></pre> <p>As a plus this library can also run in the browser.</p>

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