# react/no-unknown-property

📝 Disallow usage of unknown DOM property.

💼 This rule is enabled in the ☑️ `recommended` [config](https://github.com/jsx-eslint/eslint-plugin-react/#shareable-configs).

🔧 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix).

<!-- end auto-generated rule header -->

In JSX most DOM properties and attributes should be camelCased to be consistent with standard JavaScript style. This can be a possible source of error if you are used to writing plain HTML.
Only `data-*` and `aria-*` attributes are usings hyphens and lowercase letters in JSX.

## Rule Details

Examples of **incorrect** code for this rule:

```jsx
var React = require('react');

var Hello = <div class="hello">Hello World</div>;
var Alphabet = <div abc="something">Alphabet</div>;

// Invalid aria-* attribute
var IconButton = <div aria-foo="bar" />;
```

Examples of **correct** code for this rule:

```jsx
var React = require('react');

var Hello = <div className="hello">Hello World</div>;
var Button = <button disabled>Cannot click me</button>;
var Img = <img src={catImage} alt="A cat sleeping on a keyboard" />;

// aria-* attributes
var IconButton = <button aria-label="Close" onClick={this.close}>{closeIcon}</button>;

// data-* attributes
var Data = <div data-index={12}>Some data</div>;

// React components are ignored
var MyComponent = <App class="foo-bar"/>;
var AnotherComponent = <Foo.bar for="bar" />;

// Custom web components are ignored
var MyElem = <div class="foo" is="my-elem"></div>;
var AtomPanel = <atom-panel class="foo"></atom-panel>;
```

## Rule Options

```js
...
"react/no-unknown-property": [<enabled>, { ignore: <ignore>, requireDataLowercase: <requireDataLowercase> }]
...
```

- `enabled`: for enabling the rule. 0=off, 1=warn, 2=error. Defaults to 0.
- `ignore`: optional array of property and attribute names to ignore during validation.
- `requireDataLowercase`: optional (default: `false`), require data-\* attributes to contain only lowercase characters. React will issue a warning when data-\* attributes contain uppercase characters. In order to catch such attributes, set the `requireDataLowercase` option to `true`.

If you are using a library that passes something as a prop to JSX elements, it is recommended to add those props to the ignored properties.

For example, if you use [emotion](https://emotion.sh/docs/introduction) and its [`css` prop](https://emotion.sh/docs/css-prop),
add the following to your `.eslintrc` config file:

```js
...
"react/no-unknown-property": ['error', { ignore: ['css'] }]
...
```

Now, the following code passes:

```jsx
var StyledDiv = <div css={{ color: 'pink' }}></div>;
```

## When Not To Use It

If you are not using JSX you can disable this rule.