I'm having issues typing my code with flow. What I want to achieve is a recursive function that deep freezes and object. I have the following implementation:
const isObject: (any => boolean) = object => (
object !== null && typeof object === 'object'
)
type TObject = Object | any[]
export const deepFreeze: (TObject => TObject) = object => {
// Actually this doesn't need to be fixed, because an array is an object and
// it's properties can thus be enumerated.
// $FlowFixMe
const ownPropNames = Object.getOwnPropertyNames(object)
each(ownPropNames, name => {
const prop = object[name]
if (isObject(prop)) deepFreeze(prop)
})
return Object.freeze(object)
}
This code works for objects and arrays (which technically are objects as well) alike. But flow won't accept it, not even with the $FlowFixMe comment. Flow utters the following:
I guess this is because Object.getOwnPropertyNames is typed to only accept objects, because if I call it with an empty object instead of my variable, the errors are gone. They are also gone if I replace TObject by Object, but then of course I cannot call the function with an array. So
- why is this error message so damn confusing? It doesn't have to do anything with the problem (if I interpreted it correctly)
- why does it not accept an array, which it should, as it's an object that has enumerable property names (namely '0', '1', ..., 'length')
Suggestions would be greatly appreciated.
