Welcome back! I am Mihir, and in this lesson we will learn the Required utility type in TypeScript.

Required<T> makes every property in T required.

Basic Required Example

type UserSettings = {
  theme?: string;
  language?: string;
  notifications?: boolean;
};

type CompleteSettings = Required<UserSettings>;

CompleteSettings behaves like:

type CompleteSettings = {
  theme: string;
  language: string;
  notifications: boolean;
};

Using Required

const settings: Required<UserSettings> = {
  theme: "dark",
  language: "en",
  notifications: true,
};

Every property must be provided.

Invalid:

const settings: Required<UserSettings> = {
  theme: "dark",
};

Useful After Defaults

Required is useful when your app fills missing values with defaults.

type Config = {
  apiUrl?: string;
  timeout?: number;
};

function createConfig(config: Config): Required<Config> {
  return {
    apiUrl: config.apiUrl ?? "/api",
    timeout: config.timeout ?? 5000,
  };
}

The returned config always has all properties.

Required Does Not Remove undefined from Value Types

type Example = {
  value?: string | undefined;
};

type RequiredExample = Required<Example>;

The property becomes required, but the value type can still include undefined if it was part of the original type.

Partial and Required Together

type DraftUser = Partial<User>;
type CompleteUser = Required<DraftUser>;

This can be useful, but use it carefully. A required draft does not automatically mean the values are valid.

Quick Recap

• Required<T> makes every property required.
• It is the opposite of Partial<T>.
• It is useful after applying default values.
• It does not deeply validate runtime data.
• It does not always remove undefined from value types.

Next up, we will learn Readonly →.