<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>index</title>
<meta name="author" content="Administrator" />
<script type="text/javascript" src="yuan.js"></script>
<!-- Date: 2015-12-29 -->
<script type="text/javascript">
var r = 5;
var circle = new Circle(r);
document.write("半径为"+r+"的周长:"+circle.perimeter()+",面积："+ circle.area());
</script>
</head>
<body>
</body>
</html>
yuan.js文件代码：
/**
* 创建一个对象圆
* 属性：半径
* 方法：面积和周长
* @author Administrator
*/
function Circle(r){
this.r = r;
}
Circle.prototype.area = function(){
return this.r * this.r;
};
Circle.prototype.perimeter = function(){
return 2 * Math.PI * this.r;
};
原文：http://www.cnblogs.com/yuwensong/p/5089600.html