Rendering new component on click in react

Question

I'm practicing react and trying to render a new component on click of a button. Here the first page is email and the component i want to render contains password page.

  class App extends React.Component {
 passwordpage(){
    return(
      <form>
        <div className="mainapp">
          <h2> Password</h2>
          <input type='Password' className="inputpassword" placeholder='Enter Password' required/>
          <div>
            <button type="submit" className="loginbutton">Next</button>
          </div>
        </div>
      </form>
    );
  };

  render() {
    return (
      <form>
        <div className="mainapp">
          <h2>Email  Id</h2>
          <input type='email' ref='enteremail'className="inputemail" placeholder='Enter Username' required/>
          <div>
            <button type="submit" onClick={this.props.passwordpage} className="loginbutton">Next</button>
          </div>
        </div>
      </form>

    );
  }
}

 ReactDOM.render(<App/>,document.getElementById('app'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react-dom.min.js"></script>
<div id="app"></div>

Answer 1

The simplest is to have the password page already prepared in your render(), and to show/hide it depending on the component state, that is mutated by the onClick handler, something along those lines:

showPasswordPage() {
  this.setState({showPassword: true });
}

render() {
  const passwordPage = (<form>
    <div className="mainapp">
      <h2> Password</h2>
      <input type='Password' className="inputpassword" placeholder='Enter Password' required/>
      <div>
        <button type="submit" className="loginbutton">Next</button>
      </div>
    </div>
  </form>);

  const mainForm = (<form>
    <div className="mainapp">
      <h2>Email  Id</h2>
      <input type='email' ref='enteremail'className="inputemail" placeholder='Enter Username' required/>
      <div>
        <button type="submit" onClick={this.showPasswordPage} className="loginbutton">Next</button>
      </div>
    </div>
  </form>);

  return { this.state.showPassword ? passwordPage : mainForm };

Answer 2

I usually keep some variables in state and change them based on user action.

So in your case I have stored the current active page e.g usernamePage and when user clicks next I show another page in your case it is passwordPage.

class App extends React.Component {
  
  constructor(props) {
    super(props);

    this.state = {
      isPasswordPage : false,
      isUsernamePage : true,
      username       : "",
      password       : ""
    };

    this.enablePasswordPage  = this.enablePasswordPage.bind(this);
  }

  enablePasswordPage() {
    this.setState({
      isPasswordPage : true,
      isUsernamePage : false
    });
  }
  
  passwordpage(){
    return(
      <form>
        <div className="mainapp">
          <h2> Password</h2>
          <input type='Password' className="inputpassword" placeholder='Enter Password' required/>
          <div>
            <button type="submit" className="loginbutton">Next</button>
          </div>
        </div>
      </form>
    );
  };

  render() {
    var usernameComp = (
      <form>
        <div className="mainapp">
          <h2>Email  Id</h2>
          <input type='email' ref='enteremail'className="inputemail" placeholder='Enter Username' required/>
          <div>
            <button onClick={this.enablePasswordPage} className="loginbutton">Next</button>
          </div>
        </div>
      </form>
    );
    
    return (
      <div>
        { this.state.isUsernamePage ? usernameComp : null }
        { this.state.isPasswordPage ? this.passwordpage() : null }
      </div>
    );
  }
}

ReactDOM.render(<App/>,document.getElementById('app'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.8/react-dom.min.js"></script>
<div id="app"></div>