react-examples/conditional-greeting.htm at master · arvindpdmn/react-examples · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>React Conditional Greeting</title>
</head>

<body>
    <div id="root"></div>

    <script src="https://unpkg.com/react@15/dist/react.js"></script>
    <script src="https://unpkg.com/react-dom@15/dist/react-dom.js"></script>
    <script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>

    <script type="text/jsx">
class LoginControl extends React.Component {
  constructor(props) {
    super(props);
    this.handleLoginClick = this.handleLoginClick.bind(this);
    this.handleLogoutClick = this.handleLogoutClick.bind(this);
    this.state = {isLoggedIn: false};
  }

  handleLoginClick() {
    this.setState({isLoggedIn: true});
  }

  handleLogoutClick() {
    this.setState({isLoggedIn: false});
  }

  render() {
    const isLoggedIn = this.state.isLoggedIn;

    let button = null;
    if (isLoggedIn) {
      button = <LogoutButton onClick={this.handleLogoutClick} />;
    } else {
      button = <LoginButton onClick={this.handleLoginClick} />;
    }

    return (
      <div>
        <Greeting isLoggedIn={isLoggedIn} />
        {button}
      </div>
    );
  }
}

// This shows conditionally rendering elements
// Can conditionally render one element: put multiple ones into a div
// Example also shows how to transform array to list rendering using map()
function Mailbox(props) {
  const unreadMessages = props.unreadMessages.map((subj, i) => <li key={i}>{subj}</li>);
  return (
    <div>
      {props.unreadMessages.length > 0 &&
        <div>
          <h2>
            You have {props.unreadMessages.length} unread messages.
          </h2>
          <ul>{unreadMessages}</ul>
          {/* We can also inline the map() call:
          <ul>props.unreadMessages.map((subj, i) => <li key={i}>{subj}</li>)</ul>
          */}
        </div>
      }
    </div>
  );
}

function UserGreeting(props) {
  const messages = ['React', 'Re: React', 'Re:Re: React'];
  return (
    <div>
      <h1>Welcome back!</h1>
      <Mailbox unreadMessages={messages} />
    </div>
  );
}

function GuestGreeting(props) {
  return <h1>Please sign up.</h1>;
}

function Greeting(props) {
  const isLoggedIn = props.isLoggedIn;
  if (isLoggedIn) {
    return <UserGreeting />;
  }
  return <GuestGreeting />;
}

function LoginButton(props) {
  return (
    <button onClick={props.onClick}>
      Login
    </button>
  );
}

function LogoutButton(props) {
  return (
    <button onClick={props.onClick}>
      Logout
    </button>
  );
}

ReactDOM.render(
  <LoginControl />,
  document.getElementById('root')
);
    </script>
</body>

</html>