There's a certain amount of legacy code, because the SDK supports old browsers. Therefore it needs polyfills. And it cannot rely on, say `if ('JSON' in window){

There's a certain amount of legacy code, because the SDK supports old browsers. Therefore it needs polyfills. And it cannot rely on, say `if ('JSON' in window){}` because there are buggy polyfill implementations out there. So the SDK needs to bring its own polyfills. Additionally it cannot just do `Array.prototype.map = ...` because fiddling with the host page's globals is a sin. Hence every post-ES3 method call is wrapped in a local `ES()` function. Oh the joys of third-party javascripting :)