PropTypes in a TypeScript React Application

As @afonsoduarte said.

I'd just add that you can also generate Typescript types from PropTypes like this:

const propTypes = {
  input: PropTypes.shape({
    id: PropTypes.number.isRequired,
    name: PropTypes.string.isRequired,
  }),
};

type MyComponentProps = PropTypes.InferProps<typeof propTypes>;

const MyComponent: FunctionComponent<MyComponentProps > = (props) => {
  // ...
}

MyComponent.propTypes = propTypes;

I guess that in some messy situations where the type of the props can't be inferred at compile time, then it would be useful to see any warnings generated from using propTypes at run time.

One such situation would be when processing data from an external source for which type definitions are not available, such as an external API beyond your control. For internal APIs, I think that is worth the effort to write (or better, generate) type definitions, if they are not already available.

Other than that, I don't really see any benefit (which I why I've never used it personally).

Typescript and PropTypes serve different purposes. Typescript validates types at compile time, whereas PropTypes are checked at runtime.

Typescript is useful when you are writing code: it will warn you if you pass an argument of the wrong type to your React components, give you autocomplete for function calls, etc.

PropTypes are useful when you test how the components interact with external data, for example when you load JSON from an API. PropTypes will help you debug (when in React's Development mode) why your component is failing by printing helpful messages like:

Warning: Failed prop type: Invalid prop `id` of type `number` supplied to `Table`, expected `string`

Even though it may seem like Typescript and PropTypes do the same thing, they don't actually overlap at all. But it is possible to automatically generate PropTypes from Typescript so that you don't have to specify types twice, see for example:

• https://github.com/milesj/babel-plugin-typescript-to-proptypes
• https://github.com/grncdr/ts-react-loader#what-it-does
• https://github.com/gcanti/prop-types-ts

There's usually not much value to maintaining both your component props as TypeScript types and React.PropTypes at the same time.

Here are some cases where it is useful to do so:

• Publishing a package such as a component library that will be used by plain JavaScript.
• Accepting and passing along external input such as results from an API call.
• Using data from a library that may not have adequate or accurate typings, if any.

So, usually it's a question of how much you can trust your compile time validation.

Newer versions of TypeScript can now infer types based on your React.PropTypes (PropTypes.InferProps), but the resulting types can be difficult to use or refer to elsewhere in your code.