How to get a property type from another type alias or an interface in TypeScript?

Published January 21, 2022

To get a property type from another type alias or an interface, you can use the indexed access types feature in TypeScript.

Indexed access types are written after the type or the interface name in the form of an opening and closing square brackets symbol [], Inside the brackets we can specify the property name we need to get the type of inside quotes symbol " ".

TL;DR

// a simple interface
interface Car {
  name: string;
  yearMade: number;
}

// get the `name` property's
// type from `Car` interface
type CarName = Car["name"]; // CarName -> string

For example, let's say we have an interface called Car with a property of name having the type of string and another property called yearMade having the type of number like this,

// a simple interface
interface Car {
  name: string;
  yearMade: number;
}

Suppose we want to get the type of the name property from the Car interface. To do that let's use the indexed access type feature in TypeScript.

It can be done like this,

// a simple interface
interface Car {
  name: string;
  yearMade: number;
}

// get the `name` property's
// type from `Car` interface
type CarName = Car["name"]; // CarName -> string

Now if you hover over the CarName type you can see that its type is of string type which is the same as that of the name property's type in the Car interface.

We have successfully got the property type from another interface in TypeScript. Yay 🥳!

See the above code live in codesandbox.

That's all 😃!

Feel free to share if you found this useful 😃.


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