deep-pick

DeepPick<Type, Filter> constructs a type by picking set of properties, which have property values never or true in type Filter, from type Type

interface EnglishClass {
  students: { name: string; score: number }[];
  teacher: {
    name: string;
    yearsOfExperience: number;
  };
  year: number;
}

type EnglishClassNamesOnly = DeepPick<
  // ^? { students: { name: string }[]; teacher: { name: string }; }
  EnglishClass,
  {
    students: { name: never }[];
    teacher: {
      name: never;
    };
  }
>;

It doesn't validate that all Filter properties exist in type Type:

type UnknownEnglishClass = DeepPick<
  EnglishClass,
  {
    id: never;
    students: { id: never }[];
    teacher: {
      id: never;
    };
  }
>;

If you'd like a second type parameter Filter to be validated against a structure of a first type parameter Type, please use StrictDeepPick<Type, Filter>.

Useful in functions which cannot access specified properties

declare const englishClass: EnglishClass;

const calculateAverageScore = (englishClass: EnglishClassNamesOnly) => {
  let scoreSum = 0;

  for (const student of englishClass.students) {
    // Property 'score' does not exist on type '{ name: string; }'
    scoreSum += student.score;
    //                  ^^^^^
  }

  return scoreSum / englishClass.students.length;
};

calculateAverageScore(englishClass);

⚠️ Limitations:

• DeepPick only limits access to specified properties in your codebase, but doesn't remove them in runtime

TS Playground – https://tsplay.dev/mAJ2PW