IT人才js--碰壁反弹

这个东西倒不是很难，就是练练对临界值的判断，应该很多东西能用到这个，特别是游戏什么的

要做到临界值的判断就要获取元素的某些值，如下：

假设 obj 为某个 HTML 控件

-->obj.offsetTop 指 obj 相对于版面或由 offsetParent 属性指定的父坐标的计算上侧位置，整型，单位像素。

-->obj.offsetLeft 指 obj 相对于版面或由 offsetParent 属性指定的父坐标的计算左侧位置，整型，单位像素。

-->obj.offsetWidth 指 obj 控件自身的绝对宽度，不包括因 overflow 而未显示的部分，也就是其实际占据的宽度，整型，单位像素。

-->obj.offsetHeight 指 obj 控件自身的绝对高度，不包括因 overflow 而未显示的部分，也就是其实际占据的高度，整型，单位像素。

另外，提一个逗比的事。。。<!-- 没有offsetRight和offsetBottom -->

刚用的时候把那个用什么去了，结果什么都没获取到，幸亏问了别人一下，不然要纠结好久了，呵呵。。。

我们知道 offsetTop 可以获得 HTML 元素距离上方或外层元素的位置，style.top 也是可以的，二者的区别是：

一、offsetTop 返回的是数字，而 style.top 返回的是字符串，除了数字外还带有单位：px。

二、offsetTop 只读，而 style.top 可读写。

三、如果没有给 HTML 元素指定过 top 样式，则 style.top 返回的是空字符串。

offsetLeft 与 style.left、offsetWidth 与 style.width、offsetHeight 与 style.height 也是同样道理。

<!DOCTYPE html>

<html lang="en">

<head>

<meta charset="UTF-8">

<title>碰壁反弹</title>

<style type="text/css">

#wrap{height: 500px;width: 800px;border: 1px solid black;position: relative;}

#child{height: 50px;width: 50px;position: absolute;background: #09f;border-radius: 100%; left: 0px;}

#div1{width: 150px;height: 300px;background: #cc3;position: relative;top: 200px;left: 180px;}

#div2{width: 200px;height: 200px;background: #c33;position: relative;top: -300px;left: 600px; }

</style>

<script type="text/javascript">

window.onload=function(){

var oWrap=document.getElementById("wrap");

var oChild=document.getElementById("child");

var oDiv1=document.getElementById("div1");

var oDiv2=document.getElementById("div2");

var maxLeft=oWrap.clientWidth-oChild.offsetWidth;

var maxTop=oWrap.clientHeight-oChild.offsetHeight;

var startX=0;

var startY=0;

var x=1;

var y=1;

var left=oDiv1.offsetLeft-oChild.offsetWidth;

var right=oDiv1.offsetLeft+oDiv1.offsetWidth;

var top=oDiv1.offsetTop-oChild.offsetHeight;

var bottom=maxTop;

//var bottom=oDiv1.offsetTop+oDiv1.offsetHeight;

var left2=oDiv2.offsetLeft-oChild.offsetWidth;

var bottom2=oDiv2.offsetHeight;

function random(min,range) {

return Math.floor(Math.random() * range+min);

}

function bg() {

var a = random(0,255);

var b = random(0,255);

var c = random(0,255);

oChild.style.background = ‘rgba(‘+a+‘,‘+b+‘,‘+c+‘,0.8)‘;

// setTimeout(bg, 1000);

}

var timer=setInterval(function(){

//边线

if(startX>maxLeft||startX<0){

x*=-1;

bg();

}

if(startY>maxTop||startY<0){

y*=-1;

bg();

}

//障碍物div1

if(startX==left&&startY>top){

x*=-1;

bg();

}

if(startY==top&&startX>left&&startX<right){

y*=-1;

bg();

}

if(startX==right&&startY>top){

x*=-1;

bg();

}

//障碍物div2

if(startX==left2&&startY<bottom2){

x*=-1;

bg();

}

if(startY==bottom2&&startX>left2){

y*=-1;

bg();

}

if(startX==200&&startY==200){

x*=-1;

y*=-1;

bg();

}

if(startX==300&&startY==200){

x*=-1;

y*=-1;

bg();

}

startX+=x*5;

startY+=y*5;

oChild.style.left=startX+"px";

oChild.style.top=startY+"px";

},30)

}

</script>

</head>

<body>

</body>

<div id="wrap">

<div id="child"></div>

<div id="div1"></div>

<div id="div2"></div>

</div>

</html>

http://c.tieba.baidu.com/p/3356924842

http://c.tieba.baidu.com/p/3356926963

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时间： 2024-12-09 20:32:31

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