<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
*{
padding: 0;
margin:0;
}
html,body,main{
height: 100%;
width: 100%;
}
.box{
height: 20px;
width: 20px;
border-radius: 50%;
background:red;
position: absolute;
left: 0;
right: 0;
}
.lookFood{
font-size: 20px;
position: absolute;
left: 50%;
top:40px;
transform: translateX(-50%);
}
.food{
height: 20px;
width: 20px;
background: #faa;
border-radius: 50%;
position: absolute;
}
footer span{
position: absolute;
bottom: 20px;
left: 50%;
transform: translateX(-50%);
}
</style>
</head>
<body>
<main>
<div class="lookFood">获取了<span>0</span>个food</div>
<div class="box"></div>
<div class="food"></div>
</main>
<footer>
<span>小提示:按下↑↓←→方向键开始收集食物吧</span>
</footer>
</body>
<script>
var box = document.getElementsByClassName("box")[0],
food = document.getElementsByClassName("food")[0],
span = document.getElementsByTagName("span")[0],
//获取的食物个数
i = 0;
//初始化food的位置;每次吃到调用
function foodInit() {
food.style.left = Math.random() * parseInt(window.getComputedStyle(document.body).width) - 20 + "px";
food.style.top = Math.random() * parseInt(window.getComputedStyle(document.body).height) - 20 + "px";
//获取随机的16进制颜色值;
food.style.background = '#' + (~~(Math.random() * (1 << 24))).toString(16);
}
//小球每次运动调用这个函数 判断有没有找到食物;
function start() {
var boxLeft = parseInt(window.getComputedStyle(box).left),
boxTop = parseInt(window.getComputedStyle(box).top),
foodLeft = parseInt(window.getComputedStyle(food).left),
foodTop = parseInt(window.getComputedStyle(food).top);
//console.log(Math.abs(boxLeft - foodLeft) + "left+" + Math.abs(boxTop - foodTop) + "top+" + parseInt(window.getComputedStyle(food).height))
if (Math.abs(boxLeft - foodLeft) < parseInt(window.getComputedStyle(food).width) && Math.abs(boxTop - foodTop) < parseInt(window.getComputedStyle(food).height)) {
span.innerHTML = ++i;
foodInit()
}
}
/**
*键盘上下左右触发dom移动;
*可以同时触发两个方向的事件;
*传入四个参数:dom 需要移动的dom;
*main 移动的范围容器
*speed 每秒移动速度;
*callback 每次执行触发的函数;
*/
var keyDomMove = (function() {
//通过闭包保存变量
var keyCode = {
//每次按下上下左右的将当前按下的方向保存 为ture;
downKeyCode: function(e) {
var e = e || window.event;
//只需要用到上下左右 只保存4个键值;
if (e.keyCode === 37 || e.keyCode === 38 || e.keyCode === 39 || e.keyCode === 40) {
keyCode[e.keyCode] = true;
}
},
//每次弹起上下左右的将当前弹起的方向修改为flase;
upKeyCode: function(e) {
var e = e || window.event;
if (keyCode[e.keyCode]) {
keyCode[e.keyCode] = false;
}
},
//用于保存当前的setInterval;通过定时器增强小球移动的连贯性;
time: {},
};
return function(dom, main, speed,callback) {
if (typeof speed != "number") {
speed = 1;
} else {
//速度必须大于60px每秒;每次移动的像素小于1px 浏览器会修正为0px;这也是因为运用了定时器的缺点;
//除以60是因为浏览器播放动画每秒60帧可以保持动画的流畅性;
speed = (speed/60) > 1 ? (speed/60) : 1
}
var left = parseInt(window.getComputedStyle(dom).marginLeft),
top = parseInt(window.getComputedStyle(dom).marginTop),
mainHeigeht=parseInt(window.getComputedStyle(main).height)-20,
mainWidth=parseInt(window.getComputedStyle(main).width)-20,
//用于左右 和上下穿透;
changeXY=function(xy,min,max){
if(xy<min){
xy=max;
}else if(xy>=max){
xy=min;
}
return xy;
};
document.addEventListener("keydown", function(e) {
e.preventDefault()
keyCode.downKeyCode();
if (keyCode[37] && !keyCode.time[37]) {
keyCode.time[e.keyCode] = setInterval(function() {
var x= dom.offsetLeft - left - speed ;
x=changeXY(x,0,mainWidth);
dom.style.left =x+"px";
callback&&callback();
}, 50/3)
};
if (keyCode[38] && !keyCode.time[38]) {
keyCode.time[e.keyCode] = setInterval(function() {
var y = dom.offsetTop - top - speed
y=changeXY(y,0,mainHeigeht);
dom.style.top=y+"px";
callback&&callback();
}, 50/3)
};
if (keyCode[39] && !keyCode.time[39]) {
keyCode.time[e.keyCode] = setInterval(function() {
var x= dom.offsetLeft - left + speed ;
x=changeXY(x,0,mainWidth);
dom.style.left =x+"px";
callback&&callback();
}, 50/3)
};
if (keyCode[40] && !keyCode.time[40]) {
keyCode.time[e.keyCode] = setInterval(function() {
var y = dom.offsetTop - top + speed ;
y=changeXY(y,0,mainHeigeht);
dom.style.top=y+"px";
callback&&callback();
}, 50/3)
};
//每次弹起按键 移除当前方向的定时器 ;
document.addEventListener("keyup", function(e) {
keyCode.upKeyCode();
clearInterval(keyCode.time[e.keyCode]);
keyCode.time[e.keyCode] = null;
})
})
}
})()
function init() {
foodInit(food);
keyDomMove(box, document.body,500,start);
}
init()
</script>
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