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Table of Contents

Prerequisites

  1. good understanding of React
  2. familiarity with Typescript Types
  3. having read the Typescript section in the official React docs.
  4. (optional) Read Microsoft's TypeScript-React-Starter docs.

React + Typescript Starter Kits

  1. https://github.com/wmonk/create-react-app-typescript is the officially recommended Typescript fork of create-react-app.
  2. https://github.com/sw-yx/create-react-app-parcel-typescript sets up a React + Typescript app with Parcel :)
  3. https://github.com/basarat/typescript-react/tree/master/01%20bootstrap for manual setup of React + Typescript + Webpack + Babel

In particular, make sure that you have @types/react and @types/react-dom installed. Read more about the DefinitelyTyped project if you are unfamiliar.

Import React

import * as React from 'react';
import * as ReactDOM from 'react-dom';

In TypeScript 2.7+, you can run Typescript with --allowSyntheticDefaultImports (or add "allowSyntheticDefaultImports": true to tsconfig) to import like in regular jsx:

import React from 'react';
import ReactDOM from 'react-dom';
Explanation

Why not esModuleInterop? Daniel Rosenwasser has said that it's better for webpack/parcel. For more discussion check out wmonk/create-react-app-typescript#214

Please PR or File an issue with your suggestions!

Stateless Functional Components

You can specify the type of props as you destructure them:

const App = ({ message: string }) => <div>{message}</div>;

Or you can use the provided generic type for functional components:

const App: React.SFC<{ message: string }> = ({ message }) => <div>{message}</div>;

Quite frankly I prefer the former pattern as it's shorter.

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Stateful Class-based Components

Within Typescript, React.Component is a generic type (aka React.Component<PropType, StateType>), so you actually want to provide it with prop and (optionally) state types:

class App extends React.Component<{
  message: string, // it takes one prop called 'message' which is a string type
}> {
  render() {
    return (
      <div>{this.props.message}</div>
    );
  }
}

If the component has state, here's how to add the types for the state:

class App extends React.Component<{
  message: string, // this is the prop type
}, {
    count: number, // this is the state type
  }> {
  state = { 
    count: 0
  }
  render() {
    return (
      <div>{this.props.message} {this.state.count}</div>
    );
  }
}

If you need to define a clickhandler, just do it like normal, but just remember any arguments for your functions also need to be typed:

class App extends React.Component<{
  message: string,
}, {
    count: number,
  }> {
  state = {
    count: 0
  }
  render() {
    return (
      <div onClick={() => this.increment(1)}>{this.props.message} {this.state.count}</div>
    );
  }
  increment = (amt: number) => { // like this
    this.setState({
      count: this.state.count + amt
    });
  }
}

If you need to declare class properties for later use, just declare it with a type:

class App extends React.Component<{
  message: string,
}> {
  pointer: number // like this
  componentDidMount() {
    this.pointer = 3;
  }
  render() {
    return (
      <div>{this.props.message} and {this.pointer}</div>
    );
  }
}
Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Extracting Prop Types

Instead of defining prop types inline, you can declare them separately (useful for reusability or code organization):

type AppProps = { message: string }
const App: React.SFC<AppProps> = ({ message }) => <div>{message}</div>;

You can also do this for stateful component types (really, any types):

type AppProps = { // like this
  message: string,
}
type AppState = { // and this
  count: number,
}
class App extends React.Component<AppProps, AppState> {
  state = {
    count: 0
  }
  render() {
    return (
      <div>{this.props.message} {this.state.count}</div>
    );
  }
}

interfaces are different from types in Typescript, but for our purposes they do the same things. read more

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Basic Prop Types Examples

type AppProps = {
  message: string,
  count: number,
  disabled: boolean,
  names: string[], // array of a type!
  obj: object, // any object as long as you dont use it in your typescript code
  obj2: {}, // same
  object: {
   id: string,
   title: string
  }, // an object with defined properties
  objects: {
   id: string,
   title: string
  }[], // array of objects!
  onSomething: Function, // not recommended
  onClick: () => void, // function that doesn't return anything
  onChange: (id: number) => void, // function with named prop
  optional?: OptionalType, // an optional prop
}

Useful React Type Examples

export declare interface AppProps {
  children1: JSX.Element; // bad
  children2: JSX.Element | JSX.Element[]; // meh
  children3: React.ReactChild | React.ReactChildren; // better
  children: React.ReactNode; // best
  style?: React.CSSProperties; // for style
  onChange?: (e: React.FormEvent<HTMLInputElement>) => void; // form events!
  props: Props & React.HTMLProps<HTMLButtonElement> // to impersonate all the props of a HTML element
}
Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Forms and Events

This can be a bit tricky. The tooling really comes in handy here, as the @type definitions come with a wealth of typing. Type what you are looking for and usually the autocomplete will help you out. Here is what it looks like for an onChange for a form event:

class App extends React.Component<{}, { // no props
    text: string,
  }> {
  state = {
    text: ''
  }
  render() {
    return (
      <div>
        <input
          type="text"
          value={this.state.text}
          onChange={this.onChange}
        />
      </div>
    );
  }
  onChange = (e: React.FormEvent<HTMLInputElement>): void => {
    this.setState({text: e.currentTarget.value})
  }
}
Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Higher Order Components/Render Props

Sometimes you will want to write a function that can take a React element or a string or something else as a prop. The best Type to use for such a situation is React.ReactNode which fits anywhere a normal, well, React Node would fit:

import * as React from 'react';
export interface Props {
  label?: React.ReactNode;
  children: React.ReactNode;
}
export const Card = (props: Props) => {
  return (
    <div>
      {props.label && <div>{props.label}</div>}
      {props.children}
    </div>
  );
};

If you are using a function-as-a-child render prop:

export interface Props {
  children: (foo: string) => React.ReactNode;
}
Explanation

This is not yet written. Please PR or File an issue with your suggestions!

References/createRef

Use a React.RefObject:

class CssThemeProvider extends React.PureComponent<Props> {
  private rootRef: React.RefObject<HTMLDivElement> = React.createRef();
  render() {
    return <div ref={this.rootRef}>{this.props.children}</div>;
  }
}
Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Component/Design System Development

For developing with Storybook, read the docs I maintain over here: https://storybook.js.org/configurations/typescript-config/. This includes automatic proptype documentation generation, which is awesome :)

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Building

Please contribute on this topic! File an issue.

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Prettier + TSLint

Please contribute on this topic! File an issue.

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Working with Non-Typescript Libraries (writing your own index.d.ts)

Please contribute on this topic! File an issue.

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Troubleshooting Handbook: Types

Facing weird type errors? You aren't alone. This is the worst part of using Typescript with React. Try to avoid typing with any as much as possible to experience the full benefits of typescript. Instead, let's try to be familiar with some of the common strategies to solve these issues.

Union types

Union types are handy for solving some of these typing problems:

class App extends React.Component<{}, {
    count: number | null, // like this
  }> {
  state = {
    count: null
  }
  render() {
    return (
      <div onClick={() => this.increment(1)}>{this.state.count}</div>
    );
  }
  increment = (amt: number) => {
    this.setState({
      count: this.state.count + amt
    });
  }
}
Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Optional Types

If a component has an optional prop, add a question mark :) and assign during destructure (or use defaultProps).

class MyComponent extends React.Component<{
  message?: string, // like this
}> {
  render() {
    const {message = 'default'} = this.props;
    return (
      <div>{message}</div>
    );
  }
}

You can also use a ! character to assert that something is not undefined, but this is not encouraged.

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Enum Types

Enums in Typescript default to numbers. You will usually want to use them as strings instead:

export enum ButtonSizes {
  default = 'default',
  small = 'small',
  large = 'large'
}

Usage:

export const PrimaryButton = (
  props: Props & React.HTMLProps<HTMLButtonElement>
) => (
  <Button
    size={ButtonSizes.default}
    {...props}
  />
);

Perhaps a better alternative to enum though, is just declaring a bunch of strings with union:

export declare type Position = 'left' | 'right' | 'top' | 'bottom';
Explanation

This handy because Typescript will throw errors when you mistype a string for your props.

Type Casting

Sometimes union types need to be cast to a more specific type to work with other APIs, so cast with the as keyword.

class MyComponent extends React.Component<{
  message: string,
}> {
  render() {
    const {message} = this.props;
    return (
      <Component2 message={message as SpecialMessageType}>{message}</Component2>
    );
  }
}
Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Intersection Types

Adding two types together:

export interface Props {
  label: string;
}
export const PrimaryButton = (
  props: Props & React.HTMLProps<HTMLButtonElement> // adding my Props together with the @types/react button provided props
) => (
  <Button
    {...props}
  />
);

Omit attribute from a type

Sometimes when intersecting types, we want to define our own version of an attribute. For example, I want my component to have a label, but the type I am intersecting with also has a label attribute. Here's how to extract that out:

export interface Props {
  label: React.ReactNode // this will conflict with the InputElement's label
}

// here is the magic - omitting an attribute
type Diff<T extends string, U extends string> = ({ [P in T]: P } &
  { [P in U]: never } & { [x: string]: never })[T];
type Omit<T, K extends keyof T> = Pick<T, Diff<keyof T, K>>;
// end of magic

// usage
export const Checkbox = (
  props: Props & Omit<React.HTMLProps<HTMLInputElement>, 'label'>
) => {
  const { label } = props;
  return (
    <div className='Checkbox'>
      <label className='Checkbox-label'>
        <input
          type="checkbox"
          {...props}
        />
      </label>
      <span>{label}</span>
    </div>
  );
};
Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Troubleshooting Handbook: TSLint

Sometimes TSLint is just getting in the way. Judicious turning off of things can be helpful. Here are useful tslint disables you may use:

  • /* tslint:disable */ total disable
  • // tslint:disable-line just this line
  • /* tslint:disable:semicolon */ sometimes prettier adds semicolons and tslint doesn't like it.
  • /* tslint:disable:no-any */ disable tslint restriction on no-any when you WANT to use any
  • /* tslint:disable:max-line-length */ disable line wrapping linting

so on and so forth. there are any number of things you can disable, usually you can look at the error raised in VScode or whatever the tooling and the name of the error will correspond to the rule you should disable.

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Troubleshooting Handbook: tsconfig.json

This is the setup I roll with for my component library:

{
  "compilerOptions": {
    "outDir": "build/lib",
    "module": "commonjs",
    "target": "es5",
    "lib": ["es5", "es6", "es7", "es2017", "dom"],
    "sourceMap": true,
    "allowJs": false,
    "jsx": "react",
    "moduleResolution": "node",
    "rootDir": "src",
    "baseUrl": "src",
    "forceConsistentCasingInFileNames": true,
    "noImplicitReturns": true,
    "noImplicitThis": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "suppressImplicitAnyIndexErrors": true,
    "noUnusedLocals": true,
    "declaration": true,
    "allowSyntheticDefaultImports": true,
    "experimentalDecorators": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "build", "scripts"]
}

Please open an issue and discuss if there are better recommended choices. I like noImplicitAny to force me to type things.

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Recommended React + Typescript codebases to learn from

Explanation

This is not yet written. Please PR or File an issue with your suggestions!

Other React + Typescript resources

My question isn't answered here!

File an issue.