Rest parameters should be changed to a parameter which takes an array(e.g. ...elements: Array<T> → elements: Array<T>).
File names should be name of a method which is exported.
Leading _ is required for name of files which will be used internally.
Instance methods should be on directory <class>(e.g. Array/map).
Static methods should be on directory <class>/static(e.g. Number/static/parseInt).
Shorthands of methods should be on directory <directory which has original method>/shorthand(e.g. Array/shorthand/map, Number/static/shorthand/parseInt).
Parameter names should follow MDN Reference by default. If you think there is a better name, you can propose it.