Ensure my function returns mutated object as instanceof the same class typescript?
This solution will mutate the input object by removing the keys with undefined values.
function removeUndefined <T>(object: T): T { for (const id in object) { if (object[id] === undefined) { delete object[id]; } } return object;}It seems it works for your test case: Test in typescript playground
Yes, with each iteration of reduce you are returning a new {} which is an instance Object.
So to make the return object of same instace as of argument you should make following changes.
export const FilterUndefined = (obj) => {return Object.entries(obj).reduce((acc, [key, value]) => { if (value) {acc[key] = value;} else {delete acc[key]} return acc; }, new obj.constructor);};or you can use new obj.__proto__.constructor as per the target of typescript output you are using.
Reply in case you have typescript issues with this code snippet.