JavaScript内置对象之Math对象

2021-02-07 17:17

阅读：665

标签：class span 最小 round utf-8 随机 idt ima name

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>Documenttitle>
 7 head>
 8 body>
 9     script>
10         console.log(Math.PI);
11     script>
12 body>
13 html>

技术图片

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>Documenttitle>
 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>

技术图片

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>Documenttitle>
head>
body>
    script>
      console.log(Math.abs(-9999));
      console.log(Math.abs(9999));
      
    script>
body>
html>

技术图片

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>Documenttitle>
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>

技术图片

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>Documenttitle>
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>