Js.Obj
Utility functions on `Js.t` JS objects
let empty: unit => Js.t({.. });
let assign: Js.t({.. }) => Js.t({.. }) => Js.t({.. });
let merge: Js.t({.. }) => Js.t({.. }) => Js.t({.. });
merge obj1 obj2 assigns the properties in obj2 to a copy of obj1. The function returns a new object, and both arguments are not mutated
merge obj1 obj2
obj2
obj1
let keys: Js.t(_) => array(string);