(function (global, factory) { typeof exports === 'object' && typeof module !== 'undefined' ? factory() : typeof define === 'function' && define.amd ? define(factory) : factory(); }(this, function () { 'use strict'; var foo = {}; mutate1( foo ); // should be included [ 'a', 'b', 'c' ].forEach( function ( letter, i ) { foo[ letter ] = i; }) function mutate1 ( obj ) { obj.mutated = 1; } console.log( foo ); }));