js实现贪吃蛇游戏含注释

clearInterval(timer);
document.body.innerHTML = "";
//每秒移动多少格
let speed = 10;
let speedUpMul = 3;
//是否能穿墙
let isThroughTheWall = true;
//行数
let row = 40;
let headColor = 'red';
let bodyColor = 'green';
let foodColor = 'yellow';
let borderColor = 'grey';
// 游戏全局变量
let hasFood = false;
//游戏状态
let gamestaus = 'start';
let hasAccelerate = false;
let mainContainer = document.createElement("div");
mainContainer.style.width = 20 * row + 1 + "px";
mainContainer.style.height = 20 * row + 1 + "px";
mainContainer.style.margin = "0 auto";
mainContainer.style.position = "relative";
mainContainer.style.border = "1px solid " + borderColor;
document.body.appendChild(mainContainer);
for(let i = 0;i<row;i++){
 let marginTop = 20 * i + "px";
 for(let j = 0;j<row;j++){
 let marginLeft = j * 20 + "px";
 let tempDiv = document.createElement('div');
 tempDiv.style.width = "19px";
 tempDiv.style.height = "19px";
 tempDiv.style.marginTop = marginTop;
 tempDiv.style.marginLeft = marginLeft;
 tempDiv.style.border = "0.5px solid " + borderColor;
 tempDiv.style.position = "absolute";
 tempDiv.id = j + "div" + i;
 mainContainer.appendChild(tempDiv);
 }
}
class Cell{
 constructor(x, y, color){
 if(isThroughTheWall){
  if(x < 0) x = row-1;
  if(x > row - 1) x = 0;
  if(y < 0) y = row - 1;
  if(y > row - 1) y = 0;
 }else{
  if(x < 0 || y < 0|| x > row - 1 || y > row - 1){
  clearInterval(timer);
  alert('游戏结束');
  return;
  }
 }
 this.x = x;
 this.y = y;
 this.color = color;
 let tempDiv = document.getElementById(x + 'div' + y);
 if(tempDiv) tempDiv.style.backgroundColor = color;
 }
}
snake = {
 head : {},
 body : [],
 dire : 1
}
let headx = Math.floor(Math.random() * 14) + 3;
let heady = Math.floor(Math.random() * 14) + 3;
snake.head = new Cell(headx, heady, headColor);
//上右下左
let direction = [1, 2, 3, 4]
snake.dire = direction[Math.floor(Math.random() * 4)];
if(snake.dire == 1){
 snake.body.push(new Cell(snake.head.x, snake.head.y+1, bodyColor));
 snake.body.push(new Cell(snake.head.x, snake.head.y+2, bodyColor));
 snake.body.push(new Cell(snake.head.x, snake.head.y+3, bodyColor));
}
if(snake.dire == 2){
 snake.body.push(new Cell(snake.head.x-1, snake.head.y, bodyColor));
 snake.body.push(new Cell(snake.head.x-2, snake.head.y, bodyColor));
 snake.body.push(new Cell(snake.head.x-3, snake.head.y, bodyColor));
}
if(snake.dire == 3){
 snake.body.push(new Cell(snake.head.x, snake.head.y-1, bodyColor));
 snake.body.push(new Cell(snake.head.x, snake.head.y-2, bodyColor));
 snake.body.push(new Cell(snake.head.x, snake.head.y-3, bodyColor));
}
if(snake.dire == 4){
 snake.body.push(new Cell(snake.head.x+1, snake.head.y, bodyColor));
 snake.body.push(new Cell(snake.head.x+2, snake.head.y, bodyColor));
 snake.body.push(new Cell(snake.head.x+3, snake.head.y, bodyColor));
}
function game(){
 if(gamestaus == 'pause'){
 return;
 }
 if(gamestaus == 'gameover'){
 clearInterval(timer);
 alert('游戏结束');
 return;
 }
 initFood();
 let snakeHeadX = snake.head.x;
 let snakeHeadY = snake.head.y;
 let color = '';
 if(snake.dire == 1){
 let tempDiv = document.getElementById(snakeHeadX + 'div' + (snakeHeadY-1));
 if(tempDiv) color = tempDiv.style.backgroundColor;
 snake.head = new Cell(snakeHeadX, snakeHeadY - 1, headColor);
 }
 if(snake.dire == 2){
 let tempDiv = document.getElementById((snakeHeadX + 1) + 'div' + snakeHeadY);
 if(tempDiv) color = tempDiv.style.backgroundColor;
 snake.head = new Cell(snakeHeadX + 1, snakeHeadY, headColor);
 }
 if(snake.dire == 3){
 let tempDiv = document.getElementById(snakeHeadX + 'div' + (snakeHeadY+1));
 if(tempDiv) color = tempDiv.style.backgroundColor;
 snake.head = new Cell(snakeHeadX, snakeHeadY + 1, headColor);
 }
 if(snake.dire == 4){
 let tempDiv = document.getElementById((snakeHeadX - 1) + 'div' + snakeHeadY);
 if(tempDiv) color = tempDiv.style.backgroundColor;
 snake.head = new Cell(snakeHeadX - 1, snakeHeadY, headColor);
 }
 snake.body.unshift(new Cell(snakeHeadX, snakeHeadY, bodyColor));
 if(color && color == foodColor){
 hasFood = false;
 initFood();
 }else if(color && color == bodyColor){
 gamestaus = 'gameover'; 
 }else{
 let lastBody = snake.body.pop();
 new Cell(lastBody.x, lastBody.y, '');
 }
}
var timer = setInterval(game, 10 / speed * 100)
/**
 * 初始化食物
 */
function initFood(){
 while(!hasFood){
 let x = Math.floor(Math.random() * row);
 let y = Math.floor(Math.random() * row);
 let snakeBody = snake.body;
 let enable = true;
 if(snake.head.x == x && snake.head.y == y){
  enable = false;
 }
 for(sBody of snakeBody){
  if(sBody.x == x && sBody.y == y){
  enable = false;
  break;
  }
 }
 if(enable){
  new Cell(x, y, foodColor);
  hasFood = true;
 }
 }
}
document.onkeydown = function(e){
 if(e.keyCode == 38){
 //上
 if(snake.dire != 3 && snake.dire != 1){
  snake.dire = 1;
 }else if(snake.dire == 1){
  if(!hasAccelerate){
  clearInterval(timer);
  hasAccelerate = true;
  speed = speed * speedUpMul;
  timer = setInterval(game, 10 / speed * 100)
  }
 }
 }
 if(e.keyCode == 39){
 //右
 if(snake.dire != 4 && snake.dire != 2){
  snake.dire = 2;
 }else if(snake.dire == 2){
  if(!hasAccelerate){
  clearInterval(timer);
  hasAccelerate = true;
  speed = speed * speedUpMul;
  timer = setInterval(game, 10 / speed * 100)
  }
 }
 }
 if(e.keyCode == 40){
 //下
 if(snake.dire != 1 && snake.dire != 3){
  snake.dire = 3;
 }else if(snake.dire == 3){
  if(!hasAccelerate){
  clearInterval(timer);
  hasAccelerate = true;
  speed = speed * speedUpMul;
  timer = setInterval(game, 10 / speed * 100)
  }
 }
 }
 if(e.keyCode == 37){
 //左
 if(snake.dire != 2 && snake.dire != 4){
  snake.dire = 4;
 }else if(snake.dire == 4){
  if(!hasAccelerate){
  clearInterval(timer);
  hasAccelerate = true;
  speed = speed * speedUpMul;
  timer = setInterval(game, 10 / speed * 100)
  }
 }
 }
 //空格键暂停
 if(e.keyCode == 32){
 if(gamestaus == 'start'){
  gamestaus = 'pause';
 }else if(gamestaus == 'pause'){
  gamestaus = 'start';
 }
 }
}
document.onkeyup = function(e){
 if(e.keyCode == 38){
 //上
 if(snake.dire == 1 && hasAccelerate){
  clearInterval(timer);
  hasAccelerate = false;
  speed = speed / speedUpMul;
  timer = setInterval(game, 10 / speed * 100)
 }
 }
 if(e.keyCode == 39){
 //右
  if(snake.dire == 2 && hasAccelerate){
  clearInterval(timer);
  hasAccelerate = false;
  speed = speed / speedUpMul;
  timer = setInterval(game, 10 / speed * 100)
 }
 }
 if(e.keyCode == 40){
 //下
  if(snake.dire == 3 && hasAccelerate){
  clearInterval(timer);
  hasAccelerate = false;
  speed = speed / speedUpMul;
  timer = setInterval(game, 10 / speed * 100)
 }
 }
 if(e.keyCode == 37){
 //左
 if(snake.dire == 4 && hasAccelerate){
  clearInterval(timer);
  hasAccelerate = false;
  speed = speed / speedUpMul;
  timer = setInterval(game, 10 / speed * 100)
 }
 }
}