a cheatsheet for react users using typescript with react for the first (or nth!) time
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README.md

👋 This repo is maintained by @swyx and @IslamAttrash, we're so happy you want to try out Typescript with React! This is meant to be an intermediate guide for React developers familiar with the concepts of Typescript but who are just getting started writing their first React + Typescript apps. If you see anything wrong or missing, please file an issue! 👍

Translations: 中文翻译 maintained by @fi3ework

Table of Contents

Expand Table of Contents

Section 1: Setup

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.

    CodeSandbox has a React TypeScript template based on this project. Contributed by: @antmdvs

  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. There are also many React + Typescript boilerplates, please see our Resources list below.

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 https://github.com/wmonk/create-react-app-typescript/issues/214

Please PR or File an issue with your suggestions!

Section 2: Getting Started

Stateless Functional Components

Contributed by: @jasanst and @tpetrina

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

const App = ({ message }: { 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>;
Discussion

The former pattern is shorter, so why would people use React.SFC at all? If you need to use children property inside the function body, in the former case it has to be added explicitly. SFC<T> already includes the correctly typed children property which then doesn't have to become part of your type.

const Title: React.SFC<{ title: string }> = ({ children, title }) => (
    <div title={title}>{children}</div>
);

Something to add? File an issue.

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(state => ({
      count: 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>
    );
  }
}

Something to add? File an issue.

Typing DefaultProps

It is easy to type a defaultProps static member of a React component. There's more than one way to do it, but since we want to show the neatest code as possible we choosed to propose this way of implementing them:

interface IMyComponentProps {
  firstProp: string;
  secondProp: IPerson[];
}

export class MyComponent extends React.Component<IMyComponentProps, {}> {
  static defaultProps: Partial<IMyComponentProps> = {
    firstProp: "default",
  };
}
Explanation

This proposal is using Partial type feature in TypeScript, which means that the current interface will fullfill a partial version on the wrapped interface. In that way we can extend defaultProps without any changes in the types!

The other suggestions was related to create a new interface that will look like this:

interface IMyComponentProps {
  firstProp: string;
  secondProp: IPerson[];
}

interface IMyComponentDefaultProps {
    firstProp: string;
}

export class MyComponent extends React.Component<IMyComponentProps, {}> {
  static defaultProps: IMyComponentDefaultProps = {
    firstProp: "default",
  };
}

The problem with this approach that if we need to add another prop in the future to the defaultProps map then we should update the IMyComponentDefaultProps!

Something to add? File an issue.

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>
    );
  }
}

Something to add? File an issue.

Types or Interfaces?

interfaces are different from types in Typescript, but they can be used for very similar things as far as common React uses cases are concerned. Here's a helpful rule of thumb:

  • always use interface for public API's definition when authoring a library or 3rd party ambient type definitions.

  • consider using type for your React Component Props and State, because it is more constrained.

You can read more about the edge cases of using types and interfaces here. Note there have been significant changes since Typescript 2.1.

Something to add? File an issue.

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
}

Something to add? File an issue.

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})
  }
}

Instead of typing the arguments and return values with React.FormEvent<> and void, you may alternatively apply types to the event handler itself (contributed by @TomasHubelbauer):

  onChange: React.ChangeEventHandler<HTMLInputElement> = (e) => {
    this.setState({text: e.currentTarget.value})
  }
Discussion

Why two ways to do the same thing? The first method uses an inferred method signature (e: React.FormEvent<HTMLInputElement>): void and the second method enforces a type of the delegate provided by @types/react. So React.ChangeEventHandler<> is simply a "blessed" typing by @types/react, whereas you can think of the inferred method as more... artisanally hand-rolled. Either way it's a good pattern to know. See our Github PR for more.

Section 3: Advanced Guides

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;
}

Something to add? File an issue.

Context

Contributed by: @jpavon

Using the new context API React.createContext:

interface ProviderState {
  themeColor: string
}

interface UpdateStateArg {
  key: keyof ProviderState
  value: string
}

interface ProviderStore {
  state: ProviderState
  update: (arg: UpdateStateArg) => void
}

const Context = React.createContext({} as ProviderStore)

class Provider extends React.Component<{}, ProviderState> {
  public readonly state = {
    themeColor: 'red'
  }

  private update = ({ key, value }: UpdateStateArg) => {
    this.setState({ [key]: value })
  }

  public render() {
    const store: ProviderStore = {
      state: this.state,
      update: this.update
    }

    return (
      <Context.Provider value={store}>
        {this.props.children}
      </Context.Provider>
    )
  }
}

const Consumer = Context.Consumer

Something to add? File an issue.

Forwarding 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>;
  }
}

Something to add? File an issue.

Portals

Using ReactDOM.createPortal:

const modalRoot = document.getElementById('modal-root') as HTMLElement;
// assuming in your html file has a div with id 'modal-root';

export class Modal extends React.Component {
    el: HTMLElement = document.createElement('div');

    componentDidMount() {
        modalRoot.appendChild(this.el);
    }

    componentWillUnmount() {
        modalRoot.removeChild(this.el);
    }

    render() {
        return ReactDOM.createPortal(
            this.props.children,
            this.el
        )
    }
}
Context of Example

This example is based on the Event Bubbling Through Portal example of React docs.

Error Boundaries

Not written yet.

Something to add? File an issue.

Timeout/Placeholder/createFetcher

Not written yet. watch https://github.com/sw-yx/fresh-async-react for more on React Suspense and Time Slicing.

Something to add? File an issue.

Section 4: Misc. Concerns

Sometimes writing React isn't just about React. While we don't focus on other libraries like Redux (see below for more on that), here are some tips on other common concerns when making apps with React + Typescript.

Writing Typescript Libraries instead of Apps

propTypes may seem unnecessary with TypeScript, especially when building React + Typescript apps, but they are still relevant when writing libraries which may be used by developers working in Javascript.

interface IMyComponentProps {
  autoHeight: boolean;
  secondProp: number;
}

export class MyComponent extends React.Component<IMyComponentProps, {}> {
  static propTypes = {
    autoHeight: PropTypes.bool,
    secondProp: PropTypes.number.isRequired,
  };
}

Something to add? File an issue.

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 :)

Something to add? File an issue.

Migrating From Flow

You may wish to use https://github.com/piotrwitek/utility-types. If you have specific advice in this area, please file a PR!

Something to add? File an issue.

Prettier + TSLint

Contributed by: @azdanov

To use prettier with TSLint you will need tslint-config-prettier which disables all the conflicting rules and optionally tslint-plugin-prettier which will highlight differences as TSLint issues.

Example configuration:

tslint.json .prettierrc
{
  "rulesDirectory": ["tslint-plugin-prettier"],
  "extends": [
    "tslint:recommended",
    "tslint-config-prettier"
  ],
  "linterOptions": {
    "exclude": ["node_modules/**/*.ts"]
  },
  "rules": {
    "prettier": true
  }
}
            
{
  "printWidth": 89,
  "tabWidth": 2,
  "useTabs": false,
  "semi": true,
  "singleQuote": true,
  "trailingComma": "all",
  "bracketSpacing": true,
  "jsxBracketSameLine": false
}
            

An example github repository with a project showing how to integrate prettier + tslint + create-react-app-ts.

ESLint + TSLint

Why? ESLint ecosystem is rich, with lots of different plugins and config files, whereas TSLint tend to lag behind in some areas.

To remedy this nuisance there is an eslint-typescript-parser which tries to bridge the differences between javascript and typescript. It still has some rough corners, but can provide consistent assistance with certain plugins.

Usage .eslintrc
// Install:

npm i -D typescript-eslint-parser

// And in your ESLint configuration file:

"parser": "typescript-eslint-parser"

{
  "extends": [
    "airbnb",
    "prettier",
    "prettier/react",
    "plugin:prettier/recommended",
    "plugin:jest/recommended",
    "plugin:unicorn/recommended"
  ],
  "plugins": ["prettier", "jest", "unicorn"],
  "parserOptions": {
    "sourceType": "module",
    "ecmaFeatures": {
      "jsx": true
    }
  },
  "env": {
    "es6": true,
    "browser": true,
    "jest": true
  },
  "settings": {
    "import/resolver": {
      "node": {
        "extensions": [".js", ".jsx", ".ts", ".tsx"]
      }
    }
  },
  "overrides": [
    {
      "files": ["**/*.ts", "**/*.tsx"],
      "parser": "typescript-eslint-parser",
      "rules": {
        "no-undef": "off"
      }
    }
  ]
}
  

An example github repository with a project showing how to integrate eslint + tslint + create-react-app-ts.

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

Not written yet.

Please contribute on this topic! We have an ongoing issue here with some references.

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(state => ({
      count: (state.count || 0) + 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}
  />
);

A simpler alternative to enum is just declaring a bunch of strings with union, but this doesn't get autocompletion or syntactic benefits:

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 Assertion

Sometimes Typescript is just getting your type wrong, or union types need to be asserted to a more specific type to work with other APIs, so assert with the as keyword. This tells the compiler you know better than it does.

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

Note that this is not the same as casting.

Something to add? 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!

Type Zoo

As you can see from the Omit example above, you can write significant logic in your types as well. type-zoo is a nice toolkit of operators you may wish to check out (includes Omit), as well as utility-types (especially for those migrating from Flow).

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

React Boilerplates:

React Native Boilerplates: contributed by @spoeck

Other React + Typescript resources

My question isn't answered here!

File an issue.