React Demo

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React makes it painless to create interactive UIs. Design simple views for each state in your application, and React will efficiently update and render just the right components when your data changes. Declarative views make your code more predictable and easier to debug.

Build encapsulated components that manage their own state, then compose them to make complex UIs. Since component logic is written in JavaScript instead of templates, you can easily pass rich data through your app and keep state out of the DOM.

build an interactive tic-tac-toe game

We have three components:

  • Square
  • Board
  • Game

The Square component renders a single button, the Board renders 9 squares, and the Game component renders a board with some placeholders.

index.html

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>reactDemo</title>
    <script src="https://unpkg.com/react@latest/dist/react.js"></script>
    <script src="https://unpkg.com/react-dom@latest/dist/react-dom.js"></script>
    <script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel" src="index.js"></script>
</body>
</html>

index.js

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class Game extends React.Component{
    render() {
        return (
            <div className="game">
                <div className="game-board">
                    <Board />
                </div>
            </div>
        );
    }
}

class Board extends React.Component {
    constructor(){
        super();
        this.state = {
            squares: Array(9).fill(null),
            xIsNext: true,
        };
    }

    handleClick(i){
        const squares = this.state.squares.slice();
        if (calculateWinner(squares) || squares[i])
            return;
        squares[i] = this.state.xIsNext ? 'X' : 'O';
        this.setState({
            squares: squares,
            xIsNext: !this.state.xIsNext,
        });
    }

    renderSquare(i) {
        return (
            <Square
                value={this.state.squares[i]}
                onClick={() => this.handleClick(i)}
            />
        );
    }

    render() {
        const winner = calculateWinner(this.state.squares);
        let status;
        if (winner)
            status = 'Winner: ' + winner;
        else
            status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');

        return (
            <div>
                <div className="status">{status}</div>
                <div className="board-row">
                    {this.renderSquare(0)}
                    {this.renderSquare(1)}
                    {this.renderSquare(2)}
                </div>
                <div className="board-row">
                    {this.renderSquare(3)}
                    {this.renderSquare(4)}
                    {this.renderSquare(5)}
                </div>
                <div className="board-row">
                    {this.renderSquare(6)}
                    {this.renderSquare(7)}
                    {this.renderSquare(8)}
                </div>
            </div>
        );
    }
}

function Square(props) {
    return (
        <button className="square" onClick={props.onClick}>
            {props.value}
        </button>
    );
}

function calculateWinner(squares) {
    const lines = [
        [0, 1, 2],
        [3, 4, 5],
        [6, 7, 8],
        [0, 3, 6],
        [1, 4, 7],
        [2, 5, 8],
        [0, 4, 8],
        [2, 4, 6],
    ];

    for (let i = 0; i < lines.length; i++) {
        const [a, b, c] = lines[i];
        if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
            return squares[a];
        }
    }
    return null;
}

ReactDOM.render(
    <Game />,
    document.getElementById('root')
);

result

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