Class.jsx

class MyComponent extends Component {
  componentDidMount() {
    this.doSideEffect(this.props.foo)
  }
  
  componentDidUpdate(prev) {
    if (prev.foo !== this.props.foo) {
      this.doSideEffect(this.props.foo)
    }
  }
  
  doSideEffect = (foo) => {
    console.log(foo)
  }
  
  render() {
    return <div>Hello, world</div>
  }
}

<MyComponent foo={WHATEVER} />

Key.jsx

class MyComponent extends Component {
  componentDidMount() {
    this.doSideEffect(this.props.foo)
  }
  
  doSideEffect = (foo) => {
    console.log(foo)
  }
  
  render() {
    return <div>Hello, world</div>
  }
}

<MyComponent foo={WHATEVER} />