es6

it would be nice to start using const and let at least, but there are other interesting es6 features that could be used here, users can still use old versions of the macho module if they are using an ancient js interpreter. but all browsers support that now and it's also supported by node.

Start by reviewing the macho module's JavaScript entry points and current runtime assumptions. Identify which ES6 syntax or features are in scope, then check the module's supported Node.js and browser environments. Done means the agreed ES6 modernization is applied without dropping support for the stated older-runtime users.

Written by the indexing model from the issue text.