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Javascript to achieve snake game (including detailed notes)

  • 2021-09-04 23:06:26
  • OfStack

This article example for everyone to share Javascript to achieve snake game specific code, for your reference, the specific content is as follows

Preface

Native JavaScript to achieve snake games

GitHub address

Direct replication is available

index.html 


<!DOCTYPE html>
<html lang="en">

<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title> Greedy snake </title>
 <link rel="stylesheet" href="CSS/index.css" >
 <link rel="icon" href="favicon.ico" />
</head>

<body>
 <div class="content">
 <div class="btn startBtn"><button></button></div>
 <div class="btn pauseBtn"><button></button></div>
 <div id="snakeWrap">
 </div>
 </div>
 <script src="JS/index.js"></script>
 <script>
 // document.documentElement.style.overflow = 'hidden';
 </script>
</body>

</html>

index.css 


.content {
 width: 640px;
 height: 640px;
 margin: 100px auto;
 position: relative;
}

.btn {
 width: 100%;
 height: 100%;
 position: absolute;
 left: 0;
 top: 0;
 background-color: rgba(0, 0, 0, 0.3);
 z-index: 2;
}

.btn button {
 background: none;
 border: none;
 background-size: 100% 100%;
 cursor: pointer;
 outline: none;
 position: absolute;
 left: 50%;
 top: 50%;
}

.startBtn button {
 width: 200px;
 height: 200px;
 background-image: url(../images/startGame.png);
 margin-left: -100px;
 margin-top: -100px;

}

.pauseBtn {
 display: none;
}

.pauseBtn button {
 width: 70px;
 height: 70px;
 background-image: url(../images/pauseGame.png);
 margin-top: -35px;
 margin-left: -35px;
}

/* snakeWrap */

#snakeWrap {
 width: 600px;
 height: 600px;
 background-color: #225675;
 border: 20px solid #7dd9ff;
 position: relative;
}

#snakeWrap div {
 width: 20px;
 height: 20px;
}

.snakeHead {
 background-image: url(../images/snakeHead.png);
 background-size: cover;
 border-top-right-radius: 30%;
 border-bottom-right-radius: 30%;
}

.snakeBody {
 background-color: #9ddbb1;
 border-radius: 50%;
}

.food {
 background-image: url(../images/food.png);
 background-size: cover;
}

index. js (core part) 


var sw = 20, // 方块的宽
 sh = 20, // 方块的高
 tr = 30, // 行数
 td = 30; // 列数

var snake = null, //蛇的实例
 food = null, //食物的实例
 game = null; //游戏的实例

// 创建小方块的构造函数
// x,y代表小方块的坐标
// classname 代表等下小方块的样式
// 按照像素坐标 第1个0,0 第2个20,0 
// 但这里的x，y表示的是第1个0,0 第2个1,0
function Square(x, y, classname) {
 // 进行坐标 转换成像素坐标
 this.x = x * sw;
 this.y = y * sh;
 this.class = classname;
 this.viewContent = document.createElement('div'); // 小方块所对应的dom元素
 this.viewContent.className = this.class;
 this.parent = document.getElementById('snakeWrap'); // 方块的父级
}

Square.prototype.create = function () {
 this.viewContent.style.position = 'absolute'; // 创建方块DOM
 this.viewContent.style.width = sw + 'px';
 this.viewContent.style.height = sh + 'px';
 this.viewContent.style.left = this.x + 'px';
 this.viewContent.style.top = this.y + 'px';
 this.parent.appendChild(this.viewContent); // 将小方块添加到页面当中
};

Square.prototype.remove = function () {
 this.parent.removeChild(this.viewContent);
};

// 蛇

function Snake() {
 this.head = null; // 存1下蛇头的信息
 this.tail = null; // 存1下蛇尾的信息
 this.pos = []; // 存储蛇身上的每1个方块的位置 2维数组
 this.directionNum = {
 left: {
 x: -1,
 y: 0,
 rotate: 180 //蛇头在不同的方向中 应该进行旋转
 },
 right: {
 x: 1,
 y: 0,
 rotate: 0
 },
 up: {
 x: 0,
 y: -1,
 rotate: -90
 },
 down: {
 x: 0,
 y: 1,
 rotate: 90
 }
 }; //存储蛇走的方向 用1个对象来表示
}

Snake.prototype.init = function () {
 // 初始化
 // 创建蛇头
 var snakeHead = new Square(2, 0, 'snakeHead');
 snakeHead.create();
 this.head = snakeHead; // 存储蛇头信息
 this.pos.push([2, 0]); // 把蛇头的位置存储起来

 // 创建蛇的身体1
 var snakeBody1 = new Square(1, 0, 'snakeBody');
 snakeBody1.create();
 this.pos.push([1, 0]); //把蛇身1的坐标存储

 // 创建蛇的身体2
 var snakeBody2 = new Square(0, 0, 'snakeBody');
 snakeBody2.create();
 this.pos.push([0, 0]); //把蛇身2的坐标存储
 this.tail = snakeBody2; //存储蛇尾信息

 // 形成链表关系
 snakeHead.last = null;
 snakeHead.next = snakeBody1;

 snakeBody1.last = snakeHead;
 snakeBody1.next = snakeBody2;

 snakeBody2.last = snakeBody1;
 snakeBody2.next = null;

 // 添加1条属性，用来表示蛇走的方向
 this.direction = this.directionNum.right; // 默认让蛇往右走
};

// 这个方法用来获取蛇头的下1个位置对应的元素 
// 要根据元素做不同的事情
Snake.prototype.getNextPos = function () {
 var nextPos = [
 // 蛇头要走的下1个点的坐标
 this.head.x / sw + this.direction.x,
 this.head.y / sh + this.direction.y
 ];

 // 下1个点是自己，代表撞到了自己，游戏结束
 var selfCollied = false; //是否撞到自己
 this.pos.forEach(function (value) {
 // 数组，对象，直接比较，还要比较引用值
 if (value[0] == nextPos[0] && value[1] == nextPos[1]) {
 selfCollied = true; // 表示撞到了自己
 }
 });
 if (selfCollied) {
 // console.log('撞到自己的了');
 this.strategies.die.call(this);
 return;
 }

 // 下1个点是墙，代表撞到了围墙，游戏结束
 if (nextPos[0] < 0 || nextPos[1] < 0 || nextPos[0] > td - 1 || nextPos[1] > tr - 1) {
 // console.log('撞到墙上了');
 this.strategies.die.call(this);
 return;
 }

 // 下1个点是food，代表吃大了食物，吃

 if (food && food.pos[0] == nextPos[0] && food.pos[1] == nextPos[1]) {
 //说明蛇头要走的下1个点是食物的那个点
 // console.log('eat food');
 this.strategies.eat.call(this);
 return;
 }

 // 使用return 结束函数下面的代码运行，若是上述的情况均为发生，则最后的情况，肯定是空 

 // 下1个点是空，走
 this.strategies.move.call(this);

};

// 处理碰撞后的事件
Snake.prototype.strategies = {
 move: function (format) { // 这个参数用来决定要不要删除蛇尾 当传了操作（true）后为吃
 // 创建1个新的身体（在旧蛇头的位置）
 var newBody = new Square(this.head.x / sw, this.head.y / sh, 'snakeBody');
 // 更新链表的关系
 newBody.next = this.head.next;
 newBody.next.last = newBody;
 newBody.last = null;

 this.head.remove(); // 把旧蛇头从原来的位置删除
 newBody.create();

 // 创建1个新的蛇头,在（nextPos 位置创建）
 var newHead = new Square(this.head.x / sw + this.direction.x, this.head.y / sh + this.direction.y, 'snakeHead');
 // 更新链表的关系
 newHead.last = null;
 newHead.next = newBody;
 newHead.next.last = newHead;
 newHead.viewContent.style.transform = 'rotate(' + this.direction.rotate + 'deg)';

 newHead.create();
 // 蛇身上的每1个坐标进行更新
 this.pos.splice(0, 0, [this.head.x / sw + this.direction.x, this.head.y / sh + this.direction.y]);
 this.head = newHead; //把this.head的信息更新

 // 删除蛇尾 通过判断是否吃food，如果吃了food，就不删除，若是没有吃，就删除

 if (!format) { //如果format 的值为false 表示需要删除（除了吃之外的操作）
 this.tail.remove();
 // 更新链表
 this.tail = this.tail.last;
 this.tail.next = null;

 // 更新蛇身坐标数组
 this.pos.pop();
 }
 },
 eat: function () {
 this.strategies.move.call(this, true);
 createFood();
 game.score++;
 },
 die: function () {
 game.over();
 }
}

snake = new Snake();

// 创建食物
function createFood() {
 // 食物小方块的随机坐标
 var x = null,
 y = null;
 var include = true; // 循环跳出的条件，true表示随机生成的坐标在蛇身上，继续让他循环，false表示食物坐标不在蛇身上，不循环
 while (include) {
 // 0~29随机数
 x = Math.round(Math.random() * (td - 1))
 y = Math.round(Math.random() * (tr - 1))

 snake.pos.forEach(function (value) {
 if (value[0] != x && value[1] != y) {
 // 这个条件成立说明现在随机出的食物坐标，并未在蛇身上
 include = false;
 }
 });
 }
 // 生成食物
 food = new Square(x, y, 'food');
 food.pos = [x, y]; // 存储1下生成食物的坐标，用于跟蛇头要走的下1个点做对比 
 var foodDom = document.querySelector('.food');
 if (foodDom) {
 foodDom.style.left = x * sw + 'px';
 foodDom.style.top = y * sh + 'px';
 } else {
 food.create();
 }

}

// 创建游戏逻辑

function Game() {
 this.timer = null;
 this.score = 0;
}

Game.prototype.init = function () {
 snake.init();
 // snake.getNextPos();
 createFood();
 document.onkeydown = function (ev) {
 if (ev.which == 37 && snake.direction != snake.directionNum.right) { //用户摁下左键时候，这条蛇不能是正在往右走
 snake.direction = snake.directionNum.left;
 } else if (ev.which == 38 && snake.direction != snake.directionNum.down) {
 snake.direction = snake.directionNum.up;
 } else if (ev.which == 39 && snake.direction != snake.directionNum.left) {
 snake.direction = snake.directionNum.right;
 } else if (ev.which == 40 && snake.direction != snake.directionNum.up) {
 snake.direction = snake.directionNum.down;
 }
 }

 this.start();
}

Game.prototype.start = function () { // 开始游戏
 this.timer = setInterval(function () {
 snake.getNextPos();
 }, 200)
}

Game.prototype.pause = function () {
 clearInterval(this.timer);
}

Game.prototype.over = function () {
 clearInterval(this.timer);
 alert('你的得分为：' + this.score + '分');

 // 游戏回到最初始的状态
 var snakeWrap = document.getElementById('snakeWrap');
 snakeWrap.innerHTML = '';
 snake = new Snake();
 game = new Game();
 var startBtnWrap = document.querySelector('.startBtn');
 startBtnWrap.style.display = 'block';
}

// 开启游戏
game = new Game();
var startBtn = document.querySelector('.startBtn button');
startBtn.onclick = function () {
 startBtn.parentNode.style.display = 'none';
 game.init();
};

// 暂停
var snakeWrap = document.getElementById('snakeWrap');
var pauseBtn = document.querySelector('.pauseBtn button');
snakeWrap.onclick = function () {
 game.pause();
 pauseBtn.parentNode.style.display = 'block'
}

pauseBtn.onclick = function () {
 game.start();
 pauseBtn.parentNode.style.display = 'none';
}

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