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Last active June 6, 2021 06:09
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Basic Tic-Tac-Toe in SVG
Raw
index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>Tic Tac Toe</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" type="text/css" media="screen" href="style.css" />
</head>
<body>
<main>
<div id="game"></div>
<div id="info"></div>
</main>
<script src="tic-tac-toe.js"></script>
</body>
</html>
Raw
style.css
body {
margin: 0;
padding: 0;
font-family: sans-serif;
}
main {
display: flex;
flex-direction: row;
flex-wrap: wrap;
width: 100%;
}
line {
stroke-width: 8;
stroke-linecap: round;
}
circle {
stroke-width: 8;
fill: none;
}
.player1 {
stroke: #32BBFA;
}
.player2 {
stroke: #FA7132;
}
.grid {
stroke: #ddd;
}
#info {
margin: 50px 50px 0 0;
font-size: 2em;
}
Raw
tic-tac-toe.js
const GRID_DIMENSION = 3;
const CELL_SIZE = 100;
const MARGIN = 30;
// Helper function for creating a straight line in SVG, given its coordinates.
function createSVGLine([x1, y1], [x2, y2]) {
const line = document.createElementNS('http://www.w3.org/2000/svg', 'line');
line.setAttribute('x1', x1);
line.setAttribute('y1', y1);
line.setAttribute('x2', x2);
line.setAttribute('y2', y2);
return line;
}
// Helper function to create a cross symbol from 2 SVG lines, given its intended size. The cross is centered on [0, 0].
function createSVGCross(size) {
const g = document.createElementNS('http://www.w3.org/2000/svg', 'g');
const line1 = createSVGLine([-size, -size], [size, size]);
const line2 = createSVGLine([-size, size], [size, -size]);
g.appendChild(line1);
g.appendChild(line2);
return g;
}
class TicTacToe {
constructor() {
// 2-dimensional array to store the ID of the player whose symbol is in each grid cell. Initially all are null.
this.boardState = new Array(GRID_DIMENSION).fill(null).map(column => new Array(GRID_DIMENSION).fill(null));
// Which player's turn it is. 1 = cross, 2 = circle.
this.turn = 1;
this.gameOver = false;
this.filledSquares = 0;
this.boardView = this.initializeBoardView();
this.displayMessage('Player 1 goes first');
this.boardView.addEventListener('click', event => {
// Figure out which grid square was clicked on in this turn, and then handle that turn.
const gridX = Math.floor((event.pageX - MARGIN) / CELL_SIZE);
const gridY = Math.floor((event.pageY - MARGIN) / CELL_SIZE);
this.handleTurn(gridX, gridY);
});
}
// Set up the basic SVG for the board, including the grid lines.
initializeBoardView() {
const div = document.getElementById('game');
const boardSize = GRID_DIMENSION * CELL_SIZE;
const svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
svg.setAttribute('width', boardSize + (MARGIN * 2));
svg.setAttribute('height', boardSize + (MARGIN * 2));
div.appendChild(svg);
const board = document.createElementNS('http://www.w3.org/2000/svg', 'g');
board.setAttribute('transform', 'translate(' + MARGIN + ',' + MARGIN + ')');
svg.appendChild(board);
const rect = document.createElementNS('http://www.w3.org/2000/svg', 'rect');
rect.setAttribute('width', boardSize);
rect.setAttribute('height', boardSize);
rect.setAttribute('fill', 'white');
board.appendChild(rect);
for (let i = 1; i < GRID_DIMENSION; i++) {
let line1 = createSVGLine([CELL_SIZE * i, 0], [CELL_SIZE * i, boardSize]);
let line2 = createSVGLine([0, CELL_SIZE * i], [boardSize, CELL_SIZE * i]);
line1.setAttribute('class', 'grid');
board.appendChild(line1);
line2.setAttribute('class', 'grid');
board.appendChild(line2);
}
return board;
}
// Core game logic: deal with a click on the square [gridX, gridY].
handleTurn(gridX, gridY) {
// If the game is already over, or this square already contains a symbol, do nothing.
if (this.gameOver || this.boardState[gridX][gridY] !== null) {
return;
}
// Otherwise, add the current player's symbol to this square.
const symbol = this.createPlayerSymbol(gridX, gridY);
this.boardView.appendChild(symbol);
this.boardState[gridX][gridY] = this.turn;
this.filledSquares++;
// Check whether this symbol means that the current player has won, or the game has ended in a draw.
if (this.playerHasWon()) {
this.gameOver = true;
this.displayMessage('Player ' + this.turn + ' has won!');
} else if (this.filledSquares === GRID_DIMENSION * GRID_DIMENSION) {
this.gameOver = true;
this.displayMessage('The game ended in a draw');
} else {
// It's the other player's turn.
this.changeTurn();
}
}
changeTurn() {
this.turn = this.turn % 2 + 1;
this.displayMessage('Player ' + this.turn);
}
// Create the SVG for the symbol corresponding to the current player (1 = cross, 2 = circle).
createPlayerSymbol(gridX, gridY) {
const offset = CELL_SIZE / 2;
const symbolSize = CELL_SIZE / 5;
const g = document.createElementNS('http://www.w3.org/2000/svg', 'g');
g.setAttribute('transform', 'translate(' + (gridX * CELL_SIZE + offset) + ',' + (gridY * CELL_SIZE + offset) + ')');
g.setAttribute('class', 'player' + this.turn);
if (this.turn === 1) {
const cross = createSVGCross(symbolSize);
g.appendChild(cross);
} else {
const circle = document.createElementNS('http://www.w3.org/2000/svg', 'circle');
circle.setAttribute('r', symbolSize);
g.appendChild(circle);
}
return g;
}
// Returns true if there is any row, column, or diagonal where every cell matches the current player ID.
playerHasWon() {
// Check rows
if (this.boardState[0].some((cell, i) => this.boardState.every(row => row[i] === this.turn))) {
return true;
}
// Check columns
if (this.boardState.some(column => column.every(cell => cell === this.turn))) {
return true;
}
// Check the main diagonal
if (this.boardState.every((column, i) => this.boardState[i][i] === this.turn)) {
return true;
}
// Check the other diagonal
if (this.boardState.every((column, i) => this.boardState[i][GRID_DIMENSION - 1 - i] === this.turn)) {
return true;
}
return false;
}
displayMessage(message) {
document.getElementById('info').textContent = message;
}
}
new TicTacToe();
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