‘Higher-order functions’ is a fancy term for functions that take other functions as arguments or that return functions. Very powerful!

With Promises, developers get a standardized way to make asynchronous calls in their code. For more details about how this works, take a look at this tutorial.

In a twist of irony, a cancelable promises capability has been cancelled as a planned addition to JavaScript itself. The proposal had been championed by Google’s Dominic Denicola but had ...