Mapped types in TypeScript

Suppose you have the Car interface which allows to alter the car object’s properties once it has been created:

Under the hood TypeScript adds to each Car’s property the readonly modifier, therefore you cannot alter the id property’s value.

In fact, you could implement the Readonly type yourself:

In fact, you could implement the Partial type yourself:

In fact, you could implement the Required type yourself:

Pick

Own implementation:

Omit

Own implementation:

Since the type is not provided by TypeScript out of the box, you need to define it yourself .

I hope that this post gave you a short and clear introduction to the concept of the mapped types in TypeScript. There are situations when I find them really useful, hence it’s always worth having them in your tool belt. In addition to several mapped types provided by TypeScript, you can also create new ones yourself.

Live example:

I hope you liked the post and learned something new 👍. If so, please give me some applause 👏

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