A contrived example showing how a problem can be solved with classes or with functions in JS

FunctionalVsOop.js

/**
 * This example compares how one might go about converting an array to a string using classes or functions:
 */
const EXAMPLE_DATA = ['This', 'is', 'a', 'contrived', 'example'];

/**
 * In this first example we use a class to hold our array and a method to transform it into a string:
 */
class ArrayToStringClass {
    constructor(array) {
        this.data = array;
    }
    process() {
        let result = '';
        for (const entry of this.data) {
            result += entry + ' ';
        }
        return result;
    }
}

// Outputs: "This is a contrived example"
const processor = new ArrayToStringClass(EXAMPLE_DATA);
console.log(processor.process());

/**
 * In this second example we use a method of the array prototype called reduce and pass an anonymous function that does the array transformation.
 */
function arrayToStringReduce(array) {
    return array.reduce((accumulator, entry) => {
        return accumulator + entry + ' ';
    }, '')
}

// Outputs: "This is a contrived example"
console.log(arrayToStringReduce(EXAMPLE_DATA));

/**
 * In this final example we implement the same logic without using any methods, to give the reader a better understanding of what Array.prototype.reduce is doing.
 */
function combineEntries(previous, next) {
    return previous + next + ' ';
}

function arrayToStringSimple(array, processEntryFn, accumulator = '') {
    for(const entry of array) {
        accumulator = processEntryFn(accumulator, entry);
    }
    return accumulator;
}

// Outputs: "This is a contrived example"
console.log(arrayToStringSimple(EXAMPLE_DATA, combineEntries));