no-direct-mutation-state.md

Disallow direct mutation of this.state (react/no-direct-mutation-state)

✔️ This rule is part of the recommended config.

NEVER mutate this.state directly, as calling setState() afterwards may replace the mutation you made. Treat this.state as if it were immutable.

The only place that's acceptable to assign this.state is in a ES6 class component constructor.

Rule Details

This rule is aimed to forbid the use of mutating this.state directly.

Examples of incorrect code for this rule:

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

class Hello extends React.Component {
  constructor(props) {
    super(props)

    // Assign at instance creation time, not on a callback
    doSomethingAsync(() => {
      this.state = 'bad';
    });
  }
}

Examples of correct code for this rule:

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

class Hello extends React.Component {
  constructor(props) {
    super(props)

    this.state = {
      foo: 'bar',
    }
  }
}