eslint-plugin-react/docs/rules/prefer-stateless-function.md

Enforce stateless React Components to be written as a pure function (react/prefer-stateless-function)

Stateless functional components are simpler than class based components and will benefit from future React performance optimizations specific to these components.

Rule Details

This rule will check your class based React components for

• methods/properties other than displayName, propTypes, contextTypes, defaultProps, render and useless constructor (same detection as ESLint no-useless-constructor rule)
• instance property other than this.props and this.context
• extension of React.PureComponent (if the ignorePureComponents flag is true)
• presence of ref attribute in JSX
• the use of decorators
• render method that return anything but JSX: undefined, null, etc. (only in React <15.0.0, see shared settings for React version configuration)

If none of these elements are found, the rule will warn you to write this component as a pure function.

The following pattern is considered a warning:

var Hello = createReactClass({
  render: function() {
    return <div>Hello {this.props.name}</div>;
  }
});

The following pattern is not considered a warning:

const Foo = function(props, context) {
  const {
    location
  } = context.router;

  return <div>{props.foo}</div>;
};

The following pattern is not considered a warning in React <15.0.0:

class Foo extends React.Component {
  render() {
    if (!this.props.foo) {
      return null
    }
    return <div>{this.props.foo}</div>;
  }
}

Rule Options

...
"react/prefer-stateless-function": [<enabled>, { "ignorePureComponents": <ignorePureComponents> }]
...

• enabled: for enabling the rule. 0=off, 1=warn, 2=error. Defaults to 0.
• ignorePureComponents: optional boolean set to true to ignore components extending from React.PureComponent (default to false).

ignorePureComponents

When true the rule will ignore Components extending from React.PureComponent that use this.props or this.context.

The following pattern is considered okay and does not cause warnings:

class Foo extends React.PureComponent {
  render() {
    return <div>{this.props.foo}</div>;
  }
}

The following pattern is considered a warning because it's not using props or context:

class Foo extends React.PureComponent {
  render() {
    return <div>Bar</div>;
  }
}