The generics on Object.values and Object.entries for the value types are unsafe. They narrow the types for the value when it is unsafe to do so. Because any object is assignable to a given object type ...

However, object values may change in different environments and we then need to choose different objects accordingly. The mechanism of this environment-based value learning is unknown. To address this ...

The whole point of having a polyfill being to extend support to old browsers, it would be preferible to avoid "modern" syntax/features in the polyfill itself. Arrow function (ES6) are not supported ...