tree-shaking.js

//array.js

export function each(collection, callback) {
 //something interesting
}

export function filter(collection, callback) {
  //something interesting
  each(collection, ...)
  //something interesting
}

export function map(collection, iterator) {
  //something interesting
  each(collection, ...)
  //something interesting
}

export function reduce(collection, iterator, accumulator) {
  //something interesting
  each(collection, ...)
  //something interesting
}

//index.js
import * as Utils from ‘./utils.js’;
Utils.each([1, 2, 3], function(x) { console.log(x) });
//or
import * as Utils from ‘./utils.js’;
Utils.filter([1, 2, 3], function(x) { return x === 2 });