Homemade version of the built-in forEach() and reduce() in JavaScript

homemade-each-reduce.js

/**
 * each()
 * 
 * Apply an action to every item in an array.
 */
const list = [1, 2, 3];

const each = function (array, action) {
    for (let i = 0; i < array.length; i++) {
        action(array[i]);
    }
}

each(list, function (item) {
    console.log(`The item is: ${item}`);
});

//=> The item is: 1
//=> The item is: 2
//=> The item is: 3


/**
 * reduce()
 *
 * Reduce an array to a single value by repetitively invoking a reducer function 
 * on each item in the array, returning the final value.
 * 
 * Makes use of the above each() function.
 */
const reduce = function (array, reducer, accumulator) {
    each(array, function (item) {
        accumulator = reducer(accumulator, item);
    });
    return accumulator;
};

const sum = reduce(numbers, function (total, number) {
    return total + number;
}, 0);

console.log(`Sum: ${sum}`);  //=> 6