js实现贪吃蛇小游戏

本文实例为大家分享了js实现贪吃蛇小游戏的具体代码，供大家参考，具体内容如下

index.html

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <meta http-equiv="X-UA-Compatible" content="ie=edge">
 <title>贪吃蛇</title>
 <link rel="stylesheet" href="style.css" >
</head>
<body>
 <div id="game">
  <div id="explain">
   <div>操作WASD 空格开始/暂停 R重新开始</div>
   <div>当前分数：<span id="grade">0</span>分</div>
  </div>
  <canvas id="snakegame" width="500" height="500">
  </canvas>
 </div>
 <script type="text/javascript" src="main.js" charset="UTF-8"></script>
</body>
</html>

style.css

*{
 padding: 0;
 margin: 0;
}
#game {
 width: 500px;
 margin: auto;
}
#explain {
 width: 500px;
}
#explain div{
 width: 500px;
 height: 30px;
}
#snakegame {
 background: green;
}

main.js

/**
 * el 挂载的元素
 * attribute 贪吃蛇的属性
 */
class Game {
 constructor (el, attribute) {
  this.el = document.getElementById(el);
  // 获取画布的宽高
  this.el.elW = parseInt(window.getComputedStyle(this.el).width);
  this.el.elH = parseInt(window.getComputedStyle(this.el).height);
  this.init(attribute);
  this.keyListening();
 }
 // 初始化
 init(attribute) {
  this.attribute = {
   color: "red", // 颜色
   direction: "rigth", // 移动方向
   state: "pause", // 状态 run pause end
   grade: 0, // 分数
   body: [{x: 20, y: 0}, {x: 0, y: 0}], // 贪吃蛇身体
   wh: 20, // 矩形的宽高
   speed: 200 // 速度
  };
  if (attribute) {
   this.newAttribute = attribute;
   Object.keys(attribute).forEach(key => {
    this.attribute[key] = attribute[key];
   });
  }
  this.food ={
   x: 0,
   y: 0,
   color: 'red'
  }
  this.draw();
  this.foodDraw();
 }
 // 绘制贪吃蛇
 draw() {
  let el = this.el;
  let { body, wh, color } = this.attribute;
  // 确定浏览器是否支持canvans元素
  if (el.getContext) {
   let context = snakegame.getContext("2d");
   context.fillStyle = color;
   body.forEach( key => {
    context.fillRect(key.x, key.y, wh, wh);
   });
  }
 }
 // 随机生成食物
 foodDraw() {
  let el = this.el, wh = this.attribute.wh;
  this.food.x = Math.floor(Math.random()*(el.elW - wh)),
  this.food.y = Math.floor(Math.random()*(el.elH - wh));
  while (this.isOverlap()) {
   this.food.x = Math.floor(Math.random()*(el.elW - wh)),
   this.food.y = Math.floor(Math.random()*(el.elH - wh));
  }
  if (el.getContext) {
   let context = snakegame.getContext("2d");
   context.fillStyle = this.food.color;
   context.fillRect(this.food.x, this.food.y, wh, wh);
  }
 }
 // 判断食物是否与贪吃蛇的身体重叠
 isOverlap() {
  let { wh } = this.attribute;
  let food = this.food;
  let flag = false;
  function isIn(key, x, y) {
   if (key.x <= x && key.x + wh >= x && key.y <= y && key.y + wh >= y) {
    return true;
   } else {
    return false;
   }
  }
  this.attribute.body.forEach(key => {
   // 食物的上下左右四个点一个点在贪吃蛇的身体内就判断为重叠
   if (isIn(key, food.x, food.y) || isIn(key, food.x, food.y + wh) || isIn(key, food.x + wh, food.y) || isIn(key, food.x + wh, food.y + wh)) {
    flag = true;
   }
  });
  return flag;
 }
 // 清除图形
 clear(x, y, width, height) {
  // 确定浏览器是否支持canvans元素
  if (this.el.getContext) {
   let context = snakegame.getContext("2d");
   context.clearRect(x, y, width, height);
  }
 }
 // 游戏状态更新
 updateState(state) {
  this.attribute.state = state;
  if (state === "run") {
   this.run();
  } 
 }
 // 游戏线程
 run() {
  let { body, wh, speed} = this.attribute;
  let time = setInterval(() => {
   // 判断游戏线程是否在运行
   if (this.attribute.state !== 'run') {
    clearInterval(time);
   }
   let obj = {};
   switch(this.attribute.direction) {
    case 'left':
     obj['x'] = body[0].x - wh;
     obj['y'] = body[0].y;
     break;
    case 'rigth':
     obj['x'] = body[0].x + wh;
     obj['y'] = body[0].y;
     break;
    case 'up':
     obj['x'] = body[0].x;
     obj['y'] = body[0].y - wh;
     break;
    case 'down':
     obj['x'] = body[0].x;
     obj['y'] = body[0].y + wh;
     break;
   }
   body.unshift(obj);
   // 判断是否吃到食物 
   if (this.isOverlap()) {
    this.clear(this.food.x, this.food.y, wh, wh);
    this.attribute.grade++; 
    this.foodDraw();
    this.draw();
   } else {
    if (this.end()) {
     alert("游戏结束");
     this.updateState('end');
     clearInterval(time);
    } else {
     let item = body.pop();
     this.clear(item.x, item.y, wh, wh);
     this.draw();
    }
   }
  }, speed);
 }
 // 键盘事件监听
 keyListening() {
  document.onkeydown = (event) => {
   let e = event || window.event || arguments.callee.caller.arguments[0];
   if (e && e.keyCode === 87 && this.attribute.direction !== 'down') { // 按下W
    this.attribute.direction = 'up';
   }
   if (e && e.keyCode === 65 && this.attribute.direction !== 'rigth') { // 按下A
    this.attribute.direction = 'left';
   }
   if (e && e.keyCode === 68 && this.attribute.direction !== 'left') { // 按下D
    this.attribute.direction = 'rigth';
   }
   if (e && e.keyCode === 83 && this.attribute.direction !== 'up') { // 按下W
    this.attribute.direction = 'down';
   }
   if (e && e.keyCode === 32) { // 按下空格 
    let state;
    if (this.attribute.state === 'pause') {
     state = 'run';
    } 
    if (this.attribute.state === 'run') {
     state = 'pause';
    }
    this.updateState(state);
   }
   if (e && e.keyCode === 82) { // 按下R键
    this.reStart();
   }
  } 
 }
 // 是否死亡
 end() {
  let body = [...this.attribute.body];
  let obj = body.shift();
  let flag = false;
  if (obj.x < 0 || obj.x >= this.el.elW || obj.y < 0 || obj.y >= this.el.elH) {
   flag = true;
  }
  body.forEach(key => {
   if (key.x === obj.x && key.y === obj.y) {
    flag = true;
   }
  });
  return flag;
 }
 // 重新开始
 reStart() {
  // 清除整个画布
  this.clear(0, 0, this.el.elW, this.el.elH);
  // 重新开始
  this.init(this.newAttribute);
 }
}
let game = new Game("snakegame", {color: "yellow"});
let grade = document.getElementById("grade");
let oldGrade = game.attribute.grade;
setInterval(() => {
 if (oldGrade !== game.attribute.grade) {
  oldGrade = game.attribute.grade;
  grade.innerText = game.attribute.grade;
 }
})

截图

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