How to deep clone object properties specified in array TS/JS

Question

How to make a deep copy of an object properties specified in array. For instance i have an object {a: 1, b: 2, c: 3} And an array ["a", "b"]. I want to deeply clone only the specified properties in object, so i need to get something like this {a: 1, b: 2}. Is there an easy way to do that?

Answer 1

// By defining Keys as keys of T, you get autocompletion
// Also by setting mapped type as return you only get 
// the props you have copied in the return
const getSubset = <T, Keys extends keyof T, SubSet extends { [K in Keys]: T[K] }>(
  obj: T,
  keys: Keys[]
): SubSet => {
  return keys.reduce((acc, key) => ({ [key]: obj[key], ...acc }), <SubSet>{});
};

const object = { bio: { name: "James", age: 23 }, hobbies: ["Fishing", "Hunting", "Coding"] };
// now copy will only show you bio and not hobbies
const copy = getSubset(object, ["bio"]);
// you can mutate 
copy.bio = { name: "Jill", age: 33 };

// and it does not have side effect on original object
console.log(copy.bio, object.bio);
// prints: {name: 'Jill', age: 33} {name: 'James', age: 23}