react/no-arrow-function-lifecycle

An arrow function in a class field is created again for every instance, and it isn't on the prototype. A subclass can't call it with super.componentDidMount(), and a test can't replace it on Component.prototype. React always calls lifecycle methods on the instance, so binding this with an arrow function gains nothing.

The rule covers render, every component* and UNSAFE_component* method, shouldComponentUpdate, getSnapshotBeforeUpdate, getChildContext, getDefaultProps, getInitialState and the static getDerivedStateFromProps, in classes and in createReactClass.

--fix rewrites the arrow function as a method.

Configure#

Off by default. To turn it on:

[lint.rules]
"react/no-arrow-function-lifecycle" = "error" # or "warn"

Examples#

Reported:

class Clock extends React.Component {
  componentDidMount = () => {
    this.timer = setInterval(this.tick, 1000);
  };

  render = () => <time>{this.state.now}</time>;
}

Not reported:

class Clock extends React.Component {
  componentDidMount() {
    this.timer = setInterval(this.tick, 1000);
  }

  // Not a lifecycle method: an arrow function keeps `this` when it is passed around.
  tick = () => {
    this.setState({ now: Date.now() });
  };

  render() {
    return <time>{this.state.now}</time>;
  }
}