TypeScript

TypeScript

You can add static typing to JavaScript to improve developer productivity and code quality thanks to TypeScript.

Have a look at the Create React App with TypeScript example. A minimum version of TypeScript 2.8 is required.

Our definitions are tested with the following tsconfig.json. Using a less strict tsconfig.json or omitting some of the libraries might cause errors.

Usage of withStyles

Using withStyles in TypeScript can be a little tricky, but there are some utilities to make the experience as painless as possible.

Using createStyles to defeat type widening

A frequent source of confusion is TypeScript's type widening, which causes this example not to work as expected:

const styles = {
  root: {
    display: 'flex',
    flexDirection: 'column',
  }
};

withStyles(styles);
//         ^^^^^^
//         Types of property 'flexDirection' are incompatible.
//           Type 'string' is not assignable to type '"-moz-initial" | "inherit" | "initial" | "revert" | "unset" | "column" | "column-reverse" | "row"...'.

The problem is that the type of the flexDirection property is inferred as string, which is too arbitrary. To fix this, you can pass the styles object directly to withStyles:

withStyles({
  root: {
    display: 'flex',
    flexDirection: 'column',
  },
});

However type widening rears its ugly head once more if you try to make the styles depend on the theme:

withStyles(({ palette, spacing }) => ({
  root: {
    display: 'flex',
    flexDirection: 'column',
    padding: spacing.unit,
    backgroundColor: palette.background.default,
    color: palette.primary.main,
  },
}));

This is because TypeScript widens the return types of function expressions.

Because of this, we recommend using our createStyles helper function to construct your style rules object:

// Non-dependent styles
const styles = createStyles({
  root: {
    display: 'flex',
    flexDirection: 'column',
  },
});

// Theme-dependent styles
const styles = ({ palette, spacing }: Theme) => createStyles({
  root: {
    display: 'flex',
    flexDirection: 'column',
    padding: spacing.unit,
    backgroundColor: palette.background.default,
    color: palette.primary.main,
  },
});

createStyles is just the identity function; it doesn't "do anything" at runtime, just helps guide type inference at compile time.

Media queries

withStyles allows a styles object with top level media-queries like so:

const styles = createStyles({
  root: {
    minHeight: '100vh',
  },
  '@media (min-width: 960px)': {
    root: {
      display: 'flex',
    },
  },
});

However to allow these styles to pass TypeScript the definitions have to be ambiguous concerning names for CSS classes and actual CSS property names. Due to this class names that are equal to CSS properties should be avoided.

// error because TypeScript thinks `@media (min-width: 960px)` is a class name
// and `content` is the css property
const ambiguousStyles = createStyles({
  content: {
    minHeight: '100vh',
  },
  '@media (min-width: 960px)': {
    content: {
      display: 'flex',
    },
  },
});

// works just fine
const ambiguousStyles = createStyles({
  contentClass: {
    minHeight: '100vh',
  },
  '@media (min-width: 960px)': {
    contentClass: {
      display: 'flex',
    },
  },
});

Augmenting your props using WithStyles

Since a component decorated with withStyles(styles) gets a special classes prop injected, you will want to define its props accordingly:

const styles = (theme: Theme) => createStyles({
  root: { /* ... */ },
  paper: { /* ... */ },
  button: { /* ... */ },
});

interface Props {
  // non-style props
  foo: number;
  bar: boolean;
  // injected style props
  classes: {
    root: string;
    paper: string;
    button: string;
  };
}

However this isn't very DRY because it requires you to maintain the class names ('root', 'paper', 'button', ...) in two different places. We provide a type operator WithStyles to help with this, so that you can just write

import { WithStyles, createStyles } from '@material-ui/core';

const styles = (theme: Theme) => createStyles({
  root: { /* ... */ },
  paper: { /* ... */ },
  button: { /* ... */ },
});

interface Props extends WithStyles<typeof styles> {
  foo: number;
  bar: boolean;
}

Decorating components

Applying withStyles(styles) as a function works as expected:

const DecoratedSFC = withStyles(styles)(({ text, type, color, classes }: Props) => (
  <Typography variant={type} color={color} classes={classes}>
    {text}
  </Typography>
));

const DecoratedClass = withStyles(styles)(
  class extends React.Component<Props> {
    render() {
      const { text, type, color, classes } = this.props
      return (
        <Typography variant={type} color={color} classes={classes}>
          {text}
        </Typography>
      );
    }
  }
);

Unfortunately due to a current limitation of TypeScript decorators, withStyles(styles) can't be used as a decorator in TypeScript.

Customization of Theme

When adding custom properties to the Theme, you may continue to use it in a strongly typed way by exploiting Typescript's module augmentation.

The following example adds an appDrawer property that is merged into the one exported by material-ui:

import { Theme } from '@material-ui/core/styles/createMuiTheme';
import { Breakpoint } from '@material-ui/core/styles/createBreakpoints';

declare module '@material-ui/core/styles/createMuiTheme' {
  interface Theme {
    appDrawer: {
      width: React.CSSProperties['width']
      breakpoint: Breakpoint
    }
  }
  // allow configuration using `createMuiTheme`
  interface ThemeOptions {
    appDrawer?: {
      width?: React.CSSProperties['width']
      breakpoint?: Breakpoint
    }
  }
}

And a custom theme factory with additional defaulted options:

./styles/createMyTheme:

import createMuiTheme, { ThemeOptions } from '@material-ui/core/styles/createMuiTheme';

export default function createMyTheme(options: ThemeOptions) {
  return createMuiTheme({
    appDrawer: {
      width: 225,
      breakpoint: 'lg',
    },
    ...options,
  })
}

This could be used like:

import createMyTheme from './styles/createMyTheme';

const theme = createMyTheme({ appDrawer: { breakpoint: 'md' }});

Usage of component property

Material-UI allows you to replace a component's root node via a component property. For example, a Button's root node can be replaced with a React Router Link, and any additional props that are passed to Button, such as to, will be spread to the Link component, meaning you can do this:

import { Link } from 'react-router-dom';

<Button component={Link} to="/">Go Home</Button>

However, TypeScript will complain about it, because to is not part of the ButtonProps interface, and with the current type declarations it has no way of inferring what props can be passed to component.

The current workaround is to cast Link to any:

import { Link } from 'react-router-dom';
import Button, { ButtonProps } from '@material-ui/core/Button';

interface LinkButtonProps extends ButtonProps {
  to: string;
  replace?: boolean;
}

const LinkButton = (props: LinkButtonProps) => (
  <Button {...props} component={Link as any} />
)

// usage:
<LinkButton color="primary" to="/">Go Home</LinkButton>

Material-UI components pass some basic event handler props (onClick, onDoubleClick, etc.) to their root nodes. These handlers have a signature of:

(event: MouseEvent<HTMLElement, MouseEvent>) => void

which is incompatible with the event handler signatures that Link expects, which are:

(event: MouseEvent<AnchorElement>) => void

Any element or component that you pass into component will have this problem if the signatures of their event handler props don't match.

There is an ongoing effort to fix this by making component props generic.

Avoiding properties collision

The previous strategy suffers from a little limitation: properties collision. The component providing the component property might not forward all its properties to the root element. To workaround this issue, you can create a custom component:

import { Link } from 'react-router-dom';
import Button from '@material-ui/core/Button';

const MyLink = (props: any) => <Link to="/" {...props} />;

// usage:
<Button color="primary" component={MyLink}>Go Home</Button>