Exemplo da utilização do ciclo de vida em componentes de classe.

ClassComponentLifeCycleExample.js

import React from "react";

export default class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0,
      person: "TheAlfadur"
    };
  }

  componentDidMount() {
    console.log(this.state.count);
    console.log(this.state.person);
  }

  componentDidUpdate() {
    console.log(this.state.count);
    console.log(this.state.person);
  }

  render() {
    return (
      <>
        <button onClick={() => this.setState({ count: this.state.count + 1 })}>
          INCREMENTAR O CONTADOR
        </button>
        <button
          onClick={() =>
            this.setState({
              person:
                this.state.person === "TheAlfadur" ? "Diego" : "TheAlfadur"
            })
          }
        >
          ALTERAR PESSOA
        </button>
      </>
    );
  }
}