Discussion on: An Adequate Introduction to Functional Programming

"use strict";

function pipe(...functions) {
    // functions === [increment, double, square]

    return function(value) {
        // value === 1

        let finalValue = value;

        for (const getFunctionReturnValueFor of functions) {
            finalValue = getFunctionReturnValueFor(finalValue);
            // finalValue === increment(1) === 2
            // finalValue === double(2) === 4
            // finalValue === square(4) === 16
        }

        return finalValue;
        // finalValue === 16
    }
}

function increment(value) {
    return value + 1;
    // 1 + 1 === 2
}

function double(value) {
    return value * 2;
    // 2 * 2 === 4
}

function square(value) {
    return value ** 2;
    // 4 ** 4 === 16
}

const incDoubleSquare = pipe(increment, double, square);

console.log(incDoubleSquare(1)); // 16