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Required Utility Type

The Required<T> utility type does the opposite of Partial<T> - it forces all properties of a type to be required, even those that were originally optional.

Using `Required<T>`

Here's a practical example of using Required<T>:

interface BlogPost {
  title: string;
  content: string;
  tags?: string[];
  publishDate?: Date;
  author?: {
    id: string;
    name?: string;
  };
}

// All properties are now required
type MyRequiredBlogPost = Required<BlogPost>;

// MyRequiredBlogPost is equivalent to:
// {
//   title: string;
//   content: string;
//   tags: string[];
//   publishDate: Date;
//   author: {
//     id: string;
//     name?: string;
//   };
// }

As before, the Required<T> utility type is not recursive, it only affects the top-level properties.

Assignment

Our users' emails and phone numbers are usually optional but become required when it's time to make a purchase.

Complete the addBillingInfo function:

Use Required to enforce that the ContactInfo properties are required.
Return the string billing info: {EMAIL}, {PHONE}, replacing {EMAIL} {PHONE} with the respective fields.

Required Utility Type

Using Required<T>

Assignment

Using `Required<T>`