---
meta:
    title: React
    description: Tips for using Terra UI Components in your React app.
---

# React

Terra UI Components offers a React version of every component to provide an idiomatic experience for React users. You can easily toggle between HTML and React examples throughout the documentation.

## Installation

To add Terra UI Components to your React app, install the package from npm.

```bash
npm install @nasa-terra/components
```

Next, [include a theme](/getting-started/themes) and set the [base path](/getting-started/installation#setting-the-base-path) for icons and other assets. In this example, we'll import the light theme and use the CDN as a base path.

```jsx
// App.jsx
import '@nasa-terra/components/%NPMDIR%/themes/light.css'
import { setBasePath } from '@nasa-terra/components/%NPMDIR%/utilities/base-path'

setBasePath('https://cdn.jsdelivr.net/npm/@nasa-terra/components@%VERSION%/%CDNDIR%/')
```

:::tip
If you'd rather not use the CDN for assets, you can create a [build task](https://webpack.js.org/plugins/copy-webpack-plugin/) that copies `node_modules/@nasa-terra/components/%NPMDIR%/assets` into your app's `public` directory. Then you can point the base path to that folder instead.
:::

Now you can start using components!

### Preact

Preact users facing type errors using components may benefit from setting "paths" in their tsconfig.json so that react types will instead resolve to preact/compat as described in [Preact's typescript documentation](https://preactjs.com/guide/v10/typescript/#typescript-preactcompat-configuration).

## Usage

### Importing Components

Every Terra UI component is available to import as a React component. Note that we're importing the `<TerraButton>` _React component_ instead of the `<terra-button>` _custom element_ in the example below.

```jsx
import Button from '@nasa-terra/components/%NPMDIR%/react/button'

const MyComponent = () => <TerraButton variant="primary">Click me</TerraButton>

export default MyComponent
```

#### Notes about tree shaking

Previously, it was recommended to import from a single entrypoint like so:

```jsx
import { TerraButton } from '@nasa-terra/components/%NPMDIR%/react'
```

However, tree-shaking extra Terra components proved to be a challenge. As a result, we now recommend cherry-picking components you want to use, rather than importing from a single entrypoint.

```diff
- import { TerraButton } from '@nasa-terra/components/%NPMDIR%/react';
+ import TerraButton from '@nasa-terra/components/%NPMDIR%/react/button';
```

You can find a copy + paste import for each component in the "importing" section of its documentation.

### Event Handling

Many Terra components emit [custom events](https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent). For example, the [input component](/components/input) emits the `terra-input` event when it receives input. In React, you can listen for the event using `onTerraInput`.

Here's how you can bind the input's value to a state variable.

```jsx
import { useState } from 'react'
import TerraInput from '@nasa-terra/components/%NPMDIR%/react/input'

function MyComponent() {
    const [value, setValue] = useState('')

    return (
        <TerraInput
            value={value}
            onTerraInput={event => setValue(event.target.value)}
        />
    )
}

export default MyComponent
```

If you're using TypeScript, it's important to note that `event.target` will be a reference to the underlying custom element. You can use `(event.target as any).value` as a quick fix, or you can strongly type the event target as shown below.

```tsx
import { useState } from 'react'
import TerraInput from '@nasa-terra/components/%NPMDIR%/react/input'
import type TerraInputElement from '@nasa-terra/components/%NPMDIR%/components/input/input'

function MyComponent() {
    const [value, setValue] = useState('')

    return (
        <TerraInput
            value={value}
            onTerraInput={event =>
                setValue((event.target as TerraInputElement).value)
            }
        />
    )
}

export default MyComponent
```

You can also import the event type for use in your callbacks, shown below.

```tsx
import { useCallback, useState } from 'react'
import TerraInput, {
    type TerraInputEvent,
} from '@nasa-terra/components/%NPMDIR%/react/input'
import type TerraInputElement from '@nasa-terra/components/%NPMDIR%/components/input/input'

function MyComponent() {
    const [value, setValue] = useState('')
    const onInput = useCallback((event: TerraInputEvent) => {
        setValue(event.detail)
    }, [])

    return (
        <TerraInput
            value={value}
            onTerraInput={event =>
                setValue((event.target as TerraInputElement).value)
            }
        />
    )
}

export default MyComponent
```

## Testing with Jest

Testing with web components can be challenging if your test environment runs in a Node environment (i.e. it doesn't run in a real browser). Fortunately, [Jest](https://jestjs.io/) has made a number of strides to support web components and provide additional browser APIs. However, it's still not a complete replication of a browser environment.

Here are some tips that will help smooth things over if you're having trouble with Jest + Terra.

:::tip
If you're looking for a fast, modern testing alternative, consider [Web Test Runner](https://modern-web.dev/docs/test-runner/overview/).
:::

### Upgrade Jest

Jest underwent a major revamp and received support for web components in [version 26.5.0](https://github.com/facebook/jest/blob/main/CHANGELOG.md#2650) when it introduced [JSDOM 16.2.0](https://github.com/jsdom/jsdom/blob/master/Changelog.md#1620). This release also included a number of mocks for built-in browser functions such as `MutationObserver`, `document.createRange`, and others.

If you're using [Create React App](https://reactjs.org/docs/create-a-new-react-app.html#create-react-app), you can update `react-scripts` which will also update Jest.

```
npm install react-scripts@latest
```

### Mock Missing APIs

Some components use `window.matchMedia`, but this function isn't supported by JSDOM so you'll need to mock it yourself.

In `src/setupTests.js`, add the following.

```js
Object.defineProperty(window, 'matchMedia', {
    writable: true,
    value: jest.fn().mockImplementation(query => ({
        matches: false,
        media: query,
        onchange: null,
        addListener: jest.fn(), // deprecated
        removeListener: jest.fn(), // deprecated
        addEventListener: jest.fn(),
        removeEventListener: jest.fn(),
        dispatchEvent: jest.fn(),
    })),
})
```

For more details, refer to Jest's [manual mocking](https://jestjs.io/docs/manual-mocks#mocking-methods-which-are-not-implemented-in-jsdom) documentation.

### Transform ES Modules

ES Modules are a [well-supported browser standard](https://hacks.mozilla.org/2018/03/es-modules-a-cartoon-deep-dive/). This is how Terra is distributed, but most React apps expect CommonJS. As a result, you'll probably run into the following error.

```
Error: Unable to import outside of a module
```

To fix this, add the following to your `package.json` which tells the transpiler to process Terra modules.

```js
{
  "jest": {
    "transformIgnorePatterns": ["node_modules/(?!(@nasa/terra-ui-components))"]
  }
}
```

These instructions are for apps created via Create React App. If you're using Jest directly, you can add `transformIgnorePatterns` directly into `jest.config.js`.

For more details, refer to Jest's [`transformIgnorePatterns` customization](https://jestjs.io/docs/tutorial-react-native#transformignorepatterns-customization) documentation.

:::tip
Are you using Terra with React? [Help us improve this page!](https://github.com/nasa/terra-ui-components/blob/next/docs/frameworks/react.md)
:::
