Node.js Design Patterns

The callback pattern

Callbacks are the materialization of the handlers of the reactor pattern and they are literally one of those imprints that give Node.js its distinctive programming style. Callbacks are functions that are invoked to propagate the result of an operation and this is exactly what we need when dealing with asynchronous operations. They practically replace the use of the return instruction that, as we know, always executes synchronously. JavaScript is a great language to represent callbacks, because as we know, functions are first class objects and can be easily assigned to variables, passed as arguments, returned from another function invocation, or stored into data structures. Also, closures are an ideal construct for implementing ...