One of the interesting aspects of Javascript development is its asynchronous, event-driven nature. Any operation which will take a significant amount of time (e.g. a network request) is non-blocking. You don’t call a function and block until the operation completes. Instead functions are non-blocking - they return before the operation is complete. To obtain the result of the operation you provide callbacks which are subsequently invoked once the operation completes, allowing you to move on ...
