Calculate Average of numbers in an array in a functional way

FP.js

// Helpers
// ----------------------------------------------------------------------------
const filter  = p => a => a.filter(p);
const map     = f => a => a.map(f);
const reduce  = r => i => a => a.reduce(r, i);


// Lift for functions. to understand this use below link 👇
// See: https://jrsinclair.com/articles/2019/compose-js-functions-multiple-parameters/
const lift = f => g => h => x => f(g(x))(h(x));

// Calculations
// ----------------------------------------------------------------------------

// A sum function that adds all the items of an array together.
const sum = reduce((a, i) => a + i)(0);

// A function to get the length of an array.
const length = a => a.length;

// A function to divide one number by another.
const div = a => b => a / b;


// Usage
// ----------------------------------------------------------------------------
const ArrOfNum = [1,2,3,4,5,6,7,8]

const calcAvg = lift(div)(sum)(length)

console.log(calcAvg(ArrOfNum)) // 4.5