Reading class 3 - Alwynblake/seattle-javascript-401n12 GitHub Wiki

Notes Node.js If Google’s V8 Engine is the heart of your Node.js application, then callbacks are its veins. They enable a balanced, non-blocking flow of asynchronous control across modules and applications. But for callbacks to work at scale you’ll needed a common, reliable protocol. The “error-first” callback (also known as an “errorback”, “errback”, or “node-style callback”) was introduced to solve this problem, and has since become the standard for Node.js callbacks. / Example taken from caolan/async README async.parallel({ one: function(callback){ setTimeout(function(){ callback(null, 1); }, 200); }, two: function(callback){ setTimeout(function(){ callback(null, 2); }, 100); } }, function(err, results) { // results is equal to: {one: 1, two: 2} });