react-range/README.md

# react-range

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![Labeled Range](https://raw.githubusercontent.com/tajo/react-range/master/assets/react-range.gif?raw=true)

[![Edit react-range](https://codesandbox.io/static/img/play-codesandbox.svg)](https://codesandbox.io/s/rlp1j1183n)

[See all the other examples](https://react-range.netlify.com) and [their source code](https://github.com/tajo/react-range/tree/master/examples)!

## Installation

```
yarn add react-range
```

## Usage

```jsx
import * as React from 'react';
import { Range } from 'react-range';

class SuperSimple extends React.Component {
  state = { values: [50] };
  render() {
    return (
      <Range
        step={0.1}
        min={0}
        max={100}
        values={this.state.values}
        onChange={(values) => this.setState({ values })}
        renderTrack={({ props, children }) => (
          <div
            {...props}
            style={{
              ...props.style,
              height: '6px',
              width: '100%',
              backgroundColor: '#ccc'
            }}
          >
            {children}
          </div>
        )}
        renderThumb={({ props }) => (
          <div
            {...props}
            style={{
              ...props.style,
              height: '42px',
              width: '42px',
              backgroundColor: '#999'
            }}
          />
        )}
      />
    );
  }
}
```

## Features

- Range input supporting **vertical and horizontal sliding**
- Unopinionated styling, great for **CSS in JS** too
- No wrapping divs or additional markup, bring your own!
- **Accessible**, made for keyboards and screen readers
- **Touchable**, works on mobile devices
- Can handle negative and decimal values
- Stateless and controlled single component
- Typescript and Flow type definitions
- **No dependencies, less than 5kB (gzipped)**
- Coverage by [e2e puppeteer tests](#end-to-end-testing)
- RTL support

## Keyboard support

- `tab` and `shift+tab` to focus thumbs
- `arrow up` or `arrow right` or `k` to increase the thumb value by one step
- `arrow down` or `arrow left` or `j` to decrease the thumb value by one step
- `page up` to increase the thumb value by ten steps
- `page down` to decrease the thumb value by ten steps

## `<Range />` props

### renderTrack

```ts
renderTrack: (params: {
  props: {
    style: React.CSSProperties;
    ref: React.RefObject<any>;
    onMouseDown: (e: React.MouseEvent) => void;
    onTouchStart: (e: React.TouchEvent) => void;
  };
  children: React.ReactNode;
  isDragged: boolean;
  disabled: boolean;
}) => React.ReactNode;
```

`renderTrack` prop to define your track (root) element. **Your function gets four parameters and should return a React component**:

- `props` - this needs to be spread over the root track element, it connects mouse and touch events, adds a ref and some necessary styling
- `children` - the rendered thumbs, thumb structure should be specified in a different prop - `renderThumb`
- `isDragged` - `true` if any thumb is being dragged
- `disabled` - `true` if `<Range disabled={true} />` is set

The track can be a single narrow `div` as in the [Super simple example](https://github.com/tajo/react-range/blob/master/examples/SuperSimple.tsx); however, it might be better to use at least two nested `div`s where the outer `div` is much thicker and has a transparent background and the inner `div` is narrow, has visible background and is centered. `props` should be then spread over the outer bigger `div`. **Why to do this? It's nice to keep the `onMouseDown` and `onTouchStart` targets bigger** since the thumb can be moved also by clicking on the track (in a single thumb scenario).

### renderThumb

```ts
renderThumb: (params: {
  props: {
    key: number;
    style: React.CSSProperties;
    tabIndex?: number;
    'aria-valuemax': number;
    'aria-valuemin': number;
    'aria-valuenow': number;
    draggable: boolean;
    role: string;
    onKeyDown: (e: React.KeyboardEvent) => void;
    onKeyUp: (e: React.KeyboardEvent) => void;
  };
  value: number;
  index: number;
  isDragged: boolean;
}) => React.ReactNode;
```

`renderThumb` prop to define your thumb. **Your function gets four parameters and should return a React component**:

- `props` - it has multiple props that you need to spread over your thumb element
- `value` - a number, relative value based on `min`, `max`, `step` and the thumb's position
- `index` - the thumb index (order)
- `isDragged` - `true` if the thumb is dragged, great for styling purposes

### renderMark (optional)

```ts
renderMark?: (params: {
  props: {
    key: string;
    style: React.CSSProperties;
    ref: React.RefObject<any>;
  };
  index: number;
}) => React.ReactNode;
```

`renderMark` is an optional prop so you can render an element at each step. See this [example](https://react-range.netlify.app/?story=range--marks). **Your function gets 2 parameters and should return a React component**:

- `props` - this needs to be spread over the root track element, it adds a ref, key and some necessary styling
- `index` - index of the mark, might be useful if you want to use different styles for even/odd marks

You can use any dimensions for your marks and react-range will automatically position them at the correct place.

### values

```ts
values: number[];
```

An array of numbers. It controls the position of thumbs on the track. `values.length` equals to the number of rendered thumbs.

### onChange

```ts
onChange: (values: number[]) => void;
```

Called when a thumb is moved, provides new `values`.

### onFinalChange

```ts
onFinalChange: (values: number[]) => void;
```

Called when a change is finished (mouse/touch up, or keyup), provides current `values`. Use this event when you have to make for example ajax request with new values.

### min (optional)

```ts
min: number;
```

The range start. Can be decimal or negative. Default is `0`.

### max (optional)

```ts
max: number;
```

The range end. Can be decimal or negative. Default is `100`.

### step (optional)

```ts
step: number;
```

The minimal distance between two `values`. Can be decimal. Default is `1`.

### allowOverlap (optional)

```ts
allowOverlap: boolean;
```

When there are multiple thumbs on a single track, should they be allowed to overlap? Default is `false`.

### draggableTrack (optional)

```ts
draggableTrack: boolean;
```

When there are multiple thumbs on a single track, should it be possible to drag all thumbs at once? Default is `false`.

### direction (optional)

```ts
direction: Direction;

enum Direction {
  Right = 'to right',
  Left = 'to left',
  Down = 'to bottom',
  Up = 'to top'
}
```

It sets the orientation (vertical vs horizontal) and the direction in which the value increases. You can get this enum by:

```js
import { Direction } from 'react-range';
```

Default value is `Direction.Right`.

### disabled (optional)

```ts
disabled: boolean;
```

If `true`, it ignores all touch and mouse events and makes the component not focusable. Default is `false`.

### rtl (optional)

```ts
rtl: boolean;
```

If `true`, the slider will be optimized for RTL layouts. Default is `false`.

## getTrackBackground

There is an additional helper function being exported from `react-range`. Your track is most likely a `div` with some background. What if you want to achieve a nice "progress bar" effect where the part before the thumb has different color than the part after? What if you want to have the same thing even with multiple thumbs (aka differently colored segments)? **You don't need to glue together multiple divs in order to do that!** You can use a single `div` and set `background: linear-gradient(...)`. `getTrackBackground` function builds this verbose `linear-gradient(...)` for you!

```ts
getTrackBackground: (params: {
  min: number;
  max: number;
  values: number[];
  colors: string[];
  direction?: Direction;
  rtl?: boolean;
}) => string;
```

`min`, `max`, `values` and `direction` should be same as for the `<Range />` component. `colors` is a list of colors. This needs to be true:

```js
values.length + 1 === colors.length;
```

That's because **one thumb** (one value) splits the track into **two segments**, so you need **two colors**.

## Motivation

There is a native [input](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/range) solution:

```html
<input type="range" />
```

However, it has some serious shortcomings:

- vertical-oriented slider is [not supported in all browsers](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/range#Browser_compatibility)
- supports only a single direction
- very limited styling options
- no support for multiple thumbs

There are also many `React` based solutions but most of them are too bloated, don't support styling through CSS in JS or have lacking performance.

`react-range` has two main goals:

- **Small footprint** - less then 4kB gzipped, single component.
- **Bring your own styles and HTML markup** - `react-range` is a more low-level approach than other libraries. It doesn't come with any styling (except some positioning) or markup. It's up to the user to specify both! Think about `react-range` as a foundation for other styled input ranges.

## End to end testing

**This library is tightly coupled to many DOM APIs**. It would be very hard to ensure 100% test coverage just with unit tests that would not involve a lot of mocking. Or we could re-architect the library to better abstract all DOM interfaces but that would mean more code and bigger footprint.

Instead of that, `react-range` adds thorough end to end tests powered by [puppeteer](https://github.com/GoogleChrome/puppeteer).

All tests are automatically ran in Travis CI with headless chromium. This way, the public API is well tested, including pixel-perfect positioning. Also, the tests are pretty fast, reliable and very descriptive.

Do you want to run them in the `dev` mode (slows down operations, opens the browser)?

```bash
yarn ladle serve #start the ladle server
yarn test:e2e:dev #run the e2e tests
```

`CI` mode (ladle started on the background, quick, headless)

```bash
yarn test:e2e
```

## Browser support

- **Chrome** (latest, mac, windows, iOS, Android)
- **Firefox** (latest, mac, windows)
- **Safari** (latest, mac, iOS)
- **Edge** (latest, windows)

## Contributing

This is how you can spin up the dev environment:

```
git clone https://github.com/tajo/react-range
cd react-range
yarn
yarn ladle serve
```

## Shoutouts 🙏

Big big shoutout to **[Tom MacWright](https://macwright.org/)** for donating the `react-range` npm handle! ❤️

<img src="https://raw.githubusercontent.com/tajo/react-range/master/assets/browserstack-logo.png?raw=true" height="80" title="BrowserStack Logo" alt="BrowserStack Logo" />

Big thanks to [BrowserStack](https://www.browserstack.com) for letting the maintainers use their service to debug browser issues.

And [Netlify](https://www.netlify.com/) for free hosting.

## Author

Vojtech Miksu 2019, [miksu.cz](https://miksu.cz), [@vmiksu](https://twitter.com/vmiksu)