JS计算圆的周长和面积

叁歲伎倆 2023-10-06 08:19 25阅读 0赞

## 题目： 计算圆的周长和面积 ##

最近刚学习js，就把书上的习题做一下。

<!DOCTYPE html >
    <html>
    <head>
    
    </head>
    
    
    <body>
    	
    	<div>
    		<p>周长：<input id="zc" type="text" value="周长" ></p>
    		<p>面积：<input id="mj" type="text" value="面积" ></p>
    	</div>
    	
    <script>
    	var a = parseFloat(prompt("请输入圆的半径："))
    	const p = 3.14 //因为Π是不变的，所以我把它设为常量
    	var b = 2*p*a//周长
    	var c = a*p*a//面积
    	if(Boolean(a)){
        	//判断是否为空
    		
    		if( isNaN(a)){
        	//判断是否为数值
    		alert("输入错误")
    		}
    		else{
        
    			document.getElementById("zc").value = b.toFixed(2)//toFixed（2）化简小数点后两位
    			document.getElementById("mj").value = c.toFixed(2)
    		}
    		
    	}
    </script>
       
    </body>
    </html>

运行结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ_size_16_color_FFFFFF_t_70 1]  
小白的思路和方法，简单就好  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ_size_16_color_FFFFFF_t_70_pic_center]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200507220300161.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/202005072203006.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ_size_16_color_FFFFFF_t_70_pic_center]: https://img-blog.csdnimg.cn/20200507220612202.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDc5NzUzOQ==,size_16,color_FFFFFF,t_70#pic_center