3
index.js:182 Uncaught TypeError: document.querySelector(...).keydown is not a function
    at index.js:182

Uncaught TypeError: Cannot read property '0' of undefined
    at Snake.move (index.js:82)
    at setInterval (index.js:171)


const random = (max) => (Math.random() * (max + 1)) | 0;

let c = document.getElementById('c');
let ctx = c.getContext('2d');
let width = c.width;
let height = c.height;
let blockSize = 10;
let widthInBlocks = width / blockSize;
let heightInBlocks = height / blockSize;
let score = 0;
let drawBorder = () => {
  ctx.fillStyle = 'Gray';
  ctx.fillRect(0, 0, width, bBorderlockSize);
  ctx.fillRect(0, height - blockSize, width, blockSize);
  ctx.fillRect(width - blockSize, 0, blockSize, height);
};
let drawScore = () => {
  ctx.font = '20px Courier';
  ctx.fillStyle = 'Black';
  ctx.textAlign = 'left';
  ctx.textBaseline = 'top';
  ctx.fillText('Счет: ' + score, blockSize, blockSize);
};
let gameOver = () => {
  clearInterval(intervalId);
  ctx.font = '60px Courier';
  ctx.fillStyle = 'Black';
  ctx.textAlign = 'center';
  ctx.textBaseline = 'middle';
  ctx.fillText('Конец игры: ', width / 2, height / 2);
};
let circle = (x, y, radius, fillCircle) => {
  ctx.beginPath();
  ctx.arc(x, y, radius, 0, Math.PI * 2, false);
  if (fillCircle) {
    ctx.fill();
  } else {
    ctx.stroke();
  }
};
let Block = function(col, row) {
  this.col = col;
  this.row = row;
};
Block.prototype.drawSquare = (color) => {
  let x = this.col * blockSize;
  let y = this.row * blockSize;
  ctx.fillStyle = color;
  ctx.fillRect(x, y, blockSize, blockSize);
};
Block.prototype.drawCircle = (color) => {
  let centerX = this.col * blockSize + blockSize / 2;
  let centerY = this.row * blockSIze + blockSize / 2;
  ctx.fillStyle = color;
  circle(centerX, centerY, blockSize / 2, true);
};
Block.prototype.equal = (otherBlock) => {
  return this.col === otherBlock.col && this.row === otherBlock.row;
};
let Snake = function() {
  this.segments = [
    new Block(7, 5),
    new Block(6, 5),
    new Block(5, 5)
  ];
  this.direction = 'right';
  this.nextDirection = 'right';
};
Snake.prototype.draw = () => {
  for (let i = 0; i < this.segments.length; i++) {
    this.segments[i].drawSquare('Blue');
  }
};
Snake.prototype.move = () => {
  let head = this.segments[0];
  let newHead;
  this.direction = this.nextDirection;
  switch (this.direction) {
    case 'right':
      newHead = new Block(head.col + 1, head.row);
      break;
    case 'down':
      newHead = new Block(head.col, head.row + 1);
      break;
    case 'left':
      newHead = new Block(head.col - 1, head.row);
      break;
    case 'up':
      newHead = new Block(head.col, head.row - 1);
      break;
  };
  if (this.checkCollision(newHead)) {
    gameOver();
    return;
  }
  this.segments.unshift(newHead);
  if (newHead.equal(apple.position)) {
    score++;
    apple.move();
  } else {
    this.segments.pop()
  }
};


Snake.prototype.checkCollision = (head) => {
  let leftCollusion = (head.col === 0);
  let topCollusion = (head.row === 0);
  let rightCollusion = (head.col === widthInBlocks - 1);
  let bottomCollusion = (head.col === heightInBlocks - 1);
  let wallCollusion = leftCollusion || topCollusion || rightCollusion || bottomCollusion;
  let selfCollusion = false;
  for (let i = 0; i < this.segments.length; i++) {
    if (head.equal(this.segments[i])) {
      selfCollusion = true;
    }
  }
  return wallCollusion || selfCollusion;
};


Snake.prototype.setDirection = (newDirection) => {


if (this.direction === 'up' && newDirection === 'down') {
    return;
  } else if (this.direction === 'right' && newDirection === 'left') {
    return;
  } else if (this.direction === 'down' && newDirection === 'up') {
    return;
  } else if (this.direction === 'left' && newDirection === 'right') {
    return;
  }
  this.nextDirection = newDirection;
};
let Apple = function() {
  this.position = new Block(10, 10);
};
Apple.prototype.draw = () => {
  this.position.drawCircle('LimeGreen');
};
Apple.prototype.move = () => {
  let randomCol = Math.floor(random(widthInBlocks)) + 1;
  let randomRow = Math.floor(random(heightInBlocks)) + 1;
  this.position = new Block(randomCol, randomRow);
};
let snake = new Snake;
let apple = new Apple;


let intervalId = setInterval(() => {
  ctx.clearRect(0, 0, width, height);
  drawScore();
  snake.move();
  snake.draw();
  apple.draw();
  drawBorder();
}, 100);
let directions = {
  37: 'left',
  38: 'up',
  39: 'right',
  40: 'down'
};
document.querySelector('body').keydown((event) => {
  let newDirection = directions[event.keyCode];
  if (newDirection !== undefined) {
    snake.setDirection(newDirection);
  }
});
#canvas {
  width: 400px;
  height: 400px;
}
<canvas id="c"></canvas>
Grundy
  • 81,538
Forxz
  • 43

1 Answers1

3

Что касается первой ошибки:

document.querySelector('body').keydown((event) => {

keydown - это НЕ функция. Возможно тут сказалось влияние jQuery, в котором подписка на событие действительно выглядит так.

Для решения можно использовать метод addEventListener

document.querySelector('body').addEventListener('keydown',e => {...})

Что касается второй ошибки.

Проблема в чрезмерном увлечении стрелочными функциями.

this для стрелочных функций определяется в момент их создания (подробнее в вопросе Потеря контекста вызова)

В данном случае в момент создания, this ссылается на глобальный объект window, а не на ожидаемый объект sneak.

Решение обычное - использование в этих случаях обычных функций, а не стрелочных.

Grundy
  • 81,538