Higher-order functions in different languages. Inspired by: FizzBuzz and hello-world.

Higher-order functions (HOF) are functions that satisfy one or both rules:

• Returns a function.
• Take one or more function parameters.

The two example higher-order functions are:

add takes an integer as a parameter and returns a second function that takes an integer, which returns the overall result.

function(int) -> function(int) -> int

each is a void function takes a list as its first parameter and a function as its second parameter. It then iterates over the given list passing in each element into the function.

function([int], function(int) -> void) -> void

Show how the function is used by calling them in the program's entry point. For example:

const three = add(1)(2);
each([1, 2, 3], console.log);