I’m making a tetris game using HTML and Javascript and I would like to add the feature where you can hold blocks by pressing a key on the keyboard and if you are already holding a block then it will swap the block your holding with the block that is currently falling. How would I do this?
HTML:
<html>
<head>
<title>Tetris Clone</title>
<style>
body {
background: #202028;
color: #fff;
font-family: sans-serif;
font-size: 2em;
text-align: center;
}
canvas {
border: solid .2em #fff;
height: 90vh;
}
</style>
</head>
<body>
<div id ="score"></div>
<canvas id="tetris" width="240" height="400"></canvas>
<script src=tetris.js ></script>
</body>
</html>
Javascript:
const canvas = document.getElementById('tetris');
const context = canvas.getContext("2d");
context.scale(20, 20);
function arenaSweep() {
let rowCount = 1;
outer: for (let y = arena.length - 1; y > 0; --y) {
for (let x = 0; x < arena[y].length; ++x) {
if (arena[y][x] === 0) {
continue outer;
}
}
const row = arena.splice(y, 1)[0].fill(0);
arena.unshift(row);
++y;
player.score += rowCount * 10;
rowCount *= 2;
}
}
function collide(arena, player) {
const [m, o] = [player.matrix, player.pos];
for (let y = 0; y < m.length; ++y) {
for (let x = 0; x < m[y].length; ++x) {
if (m[y][x] !== 0 && (arena[y + o.y] && arena[y + o.y][x + o.x]) !== 0) {
return true;
}
}
}
return false;
}
function createMatrix(w, h) {
const matrix = [];
while (h--) {
matrix.push(new Array(w).fill(0));
}
return matrix
}
function createPiece(type) {
if (type === 'T') {
return [
[0, 0, 0],
[1, 1, 1],
[0, 1, 0],
];
} else if (type === 'O') {
return [
[2, 2],
[2, 2],
];
} else if (type === 'L') {
return [
[0, 3, 0],
[0, 3, 0],
[0, 3, 3],
];
} else if (type === 'J') {
return [
[0, 4, 0],
[0, 4, 0],
[4, 4, 0],
];
} else if (type === 'I') {
return [
[0, 5, 0, 0],
[0, 5, 0, 0],
[0, 5, 0, 0],
[0, 5, 0, 0],
];
} else if (type === 'S') {
return [
[0, 6, 6],
[6, 6, 0],
[0, 0, 0],
];
} else if (type === 'Z') {
return [
[7, 7, 0],
[0, 7, 7],
[0, 0, 0],
];
}
}
function draw() {
context.fillStyle = '#000';
context.fillRect(0, 0, canvas.width, canvas.height);
drawMatrix(arena, {x: 0, y: 0});
drawMatrix(player.matrix, player.pos);
}
function drawMatrix(matrix, offset) {
matrix.forEach((row, y) => {
row.forEach((value, x) => {
if (value !== 0) {
context.fillStyle = colors[value];
context.fillRect(x + offset.x, y + offset.y, 1, 1);
}
});
});
}
function merge(arena, player) {
player.matrix.forEach((row, y) => {
row.forEach((value, x) => {
if (value !== 0) {
arena[y + player.pos.y][x +player.pos.x] = value;
}
});
});
}
function playerDrop() {
player.pos.y++;
if (collide(arena, player)) {
player.pos.y--;
merge(arena, player);
playerReset();
arenaSweep();
updateScore();
}
dropCounter = 0;
}
function playerMove(dir) {
player.pos.x += dir
if (collide(arena, player)) {
player.pos.x -= dir
}
}
function playerReset() {
const pieces = 'ILJOTSZ';
player.matrix = createPiece(pieces[pieces.length * Math.random() | 0]);
player.pos.y = 0;
player.pos.x = (arena[0].length / 2 | 0) - (player.matrix[0].length / 2 | 0);
if (collide(arena, player)) {
arena.forEach(row => row.fill(0));
player.score = 0;
updateScore();
}
}
function playerRotate(dir) {
const pos = player.pos.x
let offset = 1;
rotate(player.matrix, dir)
while(collide(arena, player)) {
player.pos.x += offset;
offset = -(offset + (offset > 0 ? 1 : -1));
if (offset > player.matrix[0].length) {
rotate(player.matrix, -dir);
player.pos.x = pos;
return;
}
}
}
function rotate(matrix, dir) {
for (let y = 0; y < matrix.length; ++y) {
for (let x = 0; x < y; ++x) {
[
matrix[x][y],
matrix[y][x]
] = [
matrix[y][x],
matrix[x][y]
];
}
}
if (dir > 0) {
matrix.forEach((row => row.reverse()));
} else {
matrix.reverse();
}
}
let dropCounter = 0;
let dropInterval = 1000;
let lastTime = 0;
function update(time = 0) {
const deltaTime = time - lastTime;
lastTime = time;
dropCounter += deltaTime;
if (dropCounter > dropInterval) {
playerDrop();
}
draw();
requestAnimationFrame(update);
}
function updateScore() {
document.getElementById('score').innerText = player.score;
}
const colors = [
null,
'purple',
'yellow',
'orange',
'blue',
'cyan',
'green',
'red',
];
const arena = createMatrix(12, 20)
const player = {
pos: {x: 0, y: 0},
matrix: null,
score: 0,
}
document.addEventListener('keydown', event => {
if (event.keyCode === 37) {
playerMove(-1);
} else if (event.keyCode === 39) {
playerMove(1);
} else if (event.keyCode === 40) {
playerDrop();
} else if (event.keyCode === 90) {
playerRotate(-1);
} else if (event.keyCode === 88) {
playerRotate(1);
}
})
playerReset();
updateScore();
update();
