Node.js Design Patterns - Third Edition

3

Callbacks and Events

In synchronous programming, we conceptualize code as a series of consecutive computing steps that solve a specific problem. Every operation is blocking, which means that only when an operation is completed, it is possible to execute the next one. This approach makes the code very easy to read, understand, and debug.

On the other side, in asynchronous programming, some operations, such as reading from a file or performing a network request, are launched and then executed "in the background." When we invoke an asynchronous operation, the instruction that follows is executed immediately, even if the previous asynchronous operation has not finished yet. In this scenario, we need a way to get notified when an asynchronous operation ...