原生js实现Flappy Bird小游戏

这是一个特别简单的用原生js实现的一个小鸟游戏，比较简单，适合新手练习。

html结构

<div id="game">
 <div id="bird"></div>
</div>

css样式

#game {
   width: 800px;
   height: 600px;
   border: 1px solid #000;
   background: url(images/sky.png);
   overflow: hidden;
   position: relative;
 }

#game .pipeD {
   background: url(images/pipe1.png) top center;
   position: absolute;
 }

#game .pipeU {
   background: url(images/pipe2.png) bottom center;
   position: absolute;
 }

#bird {
   width: 34px;
   height: 25px;
   /*border-radius: 10px;*/
   /*background-color: red;*/
   position: absolute;
   top: 100px;
   left: 100px;
   background: url(images/birds.png) -8px -10px no-repeat;
 }

下面就是原生js代码了，这个小案例还运用了自己前期封装的一个小的动画方法

function animate(obj, json, fn) {
 clearInterval(obj.timer);
 obj.timer = setInterval(function () {
   var flag = true;
   for (var k in json) {
     if (k === "opacity") {
       var leader = getStyle(obj, k) * 100;
       var target = json[k] * 100;
       var step = (target - leader) / 10;
       step = step > 0 ? Math.ceil(step) : Math.floor(step);
       leader = leader + step;
       obj.style[k] = leader / 100;
     } else if (k === "zIndex") {
       obj.style.zIndex = json[k];
     } else {
       var leader = parseInt(getStyle(obj, k)) || 0;
       var target = json[k];
       var step = (target - leader) / 10;
       step = step > 0 ? Math.ceil(step) : Math.floor(step);
       leader = leader + step;
       obj.style[k] = leader + "px";
     }
     if (leader !== target) {
       flag = false;
     }
   }
   if (flag) {
     clearInterval(obj.timer);
     if (fn) {
       fn();
     }
   }
 }, 15);
}
function getStyle(obj, attr) {
 if (window.getComputedStyle) {
   return window.getComputedStyle(obj)[attr];
 } else {
   return obj.currentStyle[attr];
 }
}

下面就是控制游戏的js代码了

var birdElement = document.getElementById("bird");
var game = document.getElementById("game");
var gameover = false;
var g = 1;
var i = 0;
var timer=null;
var bird = {
 x: birdElement.offsetLeft,
 y: birdElement.offsetTop,
 speedX: 5,
 speedY: 0,
 entity: birdElement
};
var sky = {
 x: 0
};

//var timer=setInterval(function(){
//  birdElement.style.backgroundPositionX=-52*i+"px";
//  i++;
//  if(i===3){
//    i=0;
//  }
//},100);

setInterval(function () {
 //游戏没有结束的时候运行代码
 if (!gameover) {
   //整个游戏背景x轴移动的距离
   sky.x = sky.x - bird.speedX;
   game.style.backgroundPositionX = sky.x + "px";
   //小鸟下落时y轴的坐标
   bird.speedY = bird.speedY + g;
   //设置一个变量用来接收小鸟下落时y轴的坐标，用来设置小鸟下降时的速度
   var step = bird.speedY;
   bird.y = bird.y + step;
   //用一个变量来设定小鸟下落的最低高度，用来 判断游戏是否结束
   var overY = game.offsetHeight - birdElement.offsetHeight;
   //小鸟的y轴坐标大于最低高度，所以游戏停止
   if (bird.y > overY) {
     bird.y = overY;
     stop();
   }
   //小鸟的y轴坐标小于0，说明碰到顶部边框，所以游戏结束
   if (bird.y < 0) {
     bird.y = 0;
     stop();
   }
   //设置游戏开始时小鸟出现的位置
   bird.entity.style.top = bird.y + "px";
 }
}, 25);
//添加键盘事件，实现键盘上下键控制小鸟
document.onkeyup = function (e) {
 if (e.keyCode === 38) {
   bird.speedY = -10;
 }
}

function Pipe(positonX) {
 //管子的坐标
 this.x = positonX;
 this.upPipeY = 0;
 this.width = 52;
 this.upPipeH = parseInt(Math.random() * 175 + 100);
 this.downPipeY = this.upPipeH + 200;
 this.downPipeH = game.offsetHeight - this.downPipeY;
 // 动态添加管子
 var divUp = document.createElement("div");
 divUp.className = "pipeU";
 divUp.style.width = this.width + "px";
 divUp.style.height = this.upPipeH + "px";
 divUp.style.left = this.x + "px";
 divUp.style.top = this.upPipeY + "px";
 game.appendChild(divUp);
 var divDown = document.createElement("div");
 divDown.className = "pipeD";
 divDown.style.width = this.width + "px";
 divDown.style.height = this.downPipeH + "px";
 divDown.style.left = this.x + "px";
 divDown.style.top = this.downPipeY + "px";
 game.appendChild(divDown);
 //因为定时器会混乱this的指向问题，所以提前保存this的指向，这里的this指向调用该方法的实例
 var that = this;
 // 设置定时器让管子向后移动
 this.timer=setInterval(function () {
   that.x = that.x - 1;
   //简单实现管子无缝滚动
   if (that.x < -52) {
     that.x = 800;
   }
   if (!gameover) {
     divUp.style.left = that.x + "px";
     divDown.style.left = that.x + "px";
   }
   // 设置变量，进行游戏碰撞检测，并停止游戏
   var downCrash = (bird.x + 34 > that.x) && (bird.x < that.x + 52) && (bird.y + 25 > that.downPipeY);
   var upCrash = (bird.x + 34 > that.x) && (bird.x < that.x + 52) && (bird.y < that.upPipeH);
   if (downCrash || upCrash) {
     //gameover = true;
     stop();
   }
 }, 10);
}
//执行上面的函数方法
var arr=[];
for (var i = 0; i < 4; i++) {
 arr[i]=new Pipe(i * 200 + 400);
}
//封装一个用来停止游戏的方法，
function stop(){
 gameover=true;
 clearInterval(timer);
 for(var i=0;i<arr.length;i++){
   clearInterval(arr[i].timer);
 }
}

注释都写在了了代码里，一个简单小游戏就完成了。

来源：https://blog.csdn.net/qq_39081974/article/details/78134885