为什么console.log in react 运行两次

Question

Everytime I run my code on reactjs, console.log() runs twice in constructor,render, or in the components. Why does it do that?

class App extends Component {
  constructor(props){
    super(props);
    console.log("[App.js] constructor")
  }

Answer 1

You are probably using React in Strict Mode. Hence it occurs twice. This wont happen when you use production build of your react app.
This might help you further