Higher-order functions are function that can take another function as an input.

" this feature is available in a number of modern languages like JavaScript, Pascal, Swift, and a whole bunch of other ones, but it's not universal. It's not something that's available in all programming languages "

Some Wikipedia

In mathematics and computer science, a higher-order function is a function that does at least one of the following:

• takes one or more functions as arguments (i.e. procedural parameters),
• returns a function as its result.

In mathematics and computer science, a higher-order function is a function that does at least one of the following:

takes one or more functions as arguments (i.e. procedural parameters), returns a function as its result.

Code example

JavaScript

function add(a,b) { return a+b }
function multiply(a,b) { return a*b }
function calculator(a,b,operator){ return operator(a,b) }

C++

#include <iostream>

auto twice = [](auto f, int v)
{
    return f(f(v));
};

auto f = [](int i)
{
    return i + 3;
};

int main()
{   
    std::cout << twice(f, 7) << std::endl;
}

Python

>>> def twice(f):
...     def result(a):
...         return f(f(a))
...     return result

>>> plusthree = lambda x: x + 3

>>> g = twice(plusthree)

>>> g(7)