JavaScript内置对象之Math对象

Math 对象 ： JavaScript的一个内置对象

 

1.Math.PI  圆周率的值

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <title>Document</title>
 7 </head>
 8 <body>
 9     <script>
10         console.log(Math.PI);
11     </script>
12 </body>
13 </html>

 

 

2. Math.max() ,  Math.min()   取最大值最小值

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <title>Document</title>
 7 </head>
 8 <body>
 9     <script>
10        console.log(Math.max(1,2,3,4,5,6,7,8,9));
11        console.log(Math.min(1,2,3,4,5,6,7,8,9));
12     </script>
13 </body>
14 </html>

 

 

3. Math.abs()  取绝对值

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
      console.log(Math.abs(-9999));
      console.log(Math.abs(9999));
      
    </script>
</body>
</html>

 

 

4. Math.floor() 向下取整

    Math.ceil()   向上取整

    Math.round()  四舍五入取整

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
     //math.floor() 向下取整
     console.log(Math.floor(10.9));
     console.log("==========================")

     //math.ceil()   向上取整
     console.log(Math.ceil(20.2));
     console.log("==============================")
     
     //math.round()   四舍五入取整
     console.log(Math.round(4.4));
     console.log(Math.round(4.5));
     
      
    </script>
</body>
</html>

 

 

5. Math.random() 返回一个随机数   [0,1)之间的浮点数

 

返回两个数之间的一个随机整数,注意返回的这个随机数是不包含 max的，要想加上max，可以将（max - min）

修改为（max - min +1）

Math,floor(   Math.random() *( max - min ) )  + min

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        function  getRandom(min,max){
            return  Math.floor( Math.random() * (max - min) ) + min;
        }

        for(var i = 0;i <10;i++){
            console.log(getRandom(1,10));
        }
    </script>
</body>
</html>

 

posted @ 2020-04-25 18:00  瑾言**  阅读(237)  评论(0)  编辑  收藏  举报