React with TypeScript - define defaultProps in stateless function

Question

I'm using React with TypeScript and I've created stateless function. I've removed useless code from the example for readability.

interface CenterBoxProps extends React.Props<CenterBoxProps> {     minHeight?: number; }  export const CenterBox = (props: CenterBoxProps) => {     const minHeight = props.minHeight || 250;     const style = {         minHeight: minHeight     };     return <div style={style}>Example div</div>; }; 

Everything is great and this code is working correctly. But there's my question: how can I define defaultProps for CenterBox component?

As it is mentioned in react docs:

(...) They are pure functional transforms of their input, with zero boilerplate. However, you may still specify .propTypes and .defaultProps by setting them as properties on the function, just as you would set them on an ES6 class. (...)

it should be easy as:

CenterBox.defaultProps = {     minHeight: 250 } 

But this code generates TSLint error: error TS2339: Property 'defaultProps' does not exist on type '(props: CenterBoxProps) => Element'.

So again: how can I correctly define defaultProps in my above stack (React + TypeScript)?

Answer 1

After 2 hours of looking for solution... it's working.

If you want to define defaultProps, your arrow function should look like:

export const CenterBox: React.SFC<CenterBoxProps> = props => {     (...) }; 

Then you can define props like:

CenterBox.defaultProps = { someProp: true } 

Note that React.SFC is alias for React.StatelessComponent.

I hope that this question (and answer) help somebody. Make sure that you have installed newest React typings.

Answer 2

I believe a better way than described in the React docs is simply to use Javascript / Typescript default arguments.

There's an answer here: https://stackoverflow.com/a/54569933/484190 but for convenience, here's an example:

import React, { FC } from "react";  interface CompProps {   x?: number;   y?: number; }  const Comp: FC<CompProps> = ({ x = 10, y = 20 }) => {   return <div>{x}, {y}</div>; }  export default Comp; 

This will allow Typescript to know that you don't have to provide the prop, and also that it will never be "undefined" inside your component