no-this-in-sfc.md

Disallow this from being used in stateless functional components (react/no-this-in-sfc)

In React, there are two styles of component. One is a class component: class Foo extends React.Component {...}, which accesses its props, context, and state as properties of this: this.props.foo, etc. The other are stateless functional components (SFCs): function Foo(props, context) {...}. As you can see, there's no state (hence the name - hooks do not change this), and the props and context are provided as its two functional arguments. In an SFC, state is usually best implements with a React hook such as React.useState().

Attempting to access properties on this can sometimes be valid, but it's very commonly an error caused by unfamiliarity with the differences between the two styles of components, or a missed reference when converting a class component to an SFC.

Rule Details

Examples of incorrect code for this rule:

function Foo(props) {
  return (
    <div>{this.props.bar}</div>
  );
}

function Foo(props) {
  const { bar } = this.props;
  return (
    <div>{bar}</div>
  );
}

function Foo(props, context) {
  return (
    <div>
      {this.context.foo ? this.props.bar : ''}
    </div>
  );
}

function Foo(props, context) {
  const { foo } = this.context;
  const { bar } = this.props;
  return (
    <div>
      {foo ? bar : ''}
    </div>
  );
}

function Foo(props) {
  if (this.state.loading) {
    return <Loader />;
  }
  return (
    <div>
      {this.props.bar}
    </div>
  );
}

function Foo(props) {
  const { loading } = this.state;
  const { bar } = this.props;
  if (loading) {
    return <Loader />;
  }
  return (
    <div>
      {bar}
    </div>
  );
}

Examples of correct code for this rule:

function Foo(props) {
  return (
    <div>{props.bar}</div>
  );
}

function Foo(props) {
  const { bar } = props;
  return (
    <div>{bar}</div>
  );
}

function Foo({ bar }) {
  return (
    <div>{bar}</div>
  );
}

function Foo(props, context) {
  return (
    <div>
      {context.foo ? props.bar : ''}
    </div>
  );
}

function Foo(props, context) {
  const { foo } = context;
  const { bar } = props;
  return (
    <div>
      {foo ? bar : ''}
    </div>
  );
}

function Foo({ bar }, { foo }) {
  return (
    <div>
      {foo ? bar : ''}
    </div>
  );
}