If you write JavaScript, you have probably used higher-order functions and not even noticed. If you have ever replaced a for loop with an array method, you’ve used higher-order functions.

Let's look at each of these in more detail. Functions are first-class citizens In functional programming, functions are treated as first-class citizens. Functional programming supports higher-order ...

Unfortunately, this function immediately “forgets” the second value and never does anything with it. Our inner function, the one that currently just returns value1, also needs to be modified ...