Math.max() 最大值
    Math.min() 最小值
    Math.ceil() 上取整
    Math.floor() 下取整
    Math.round() 四舍五入取整
    Math.random() 随机数 0<num<1

    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.         /* 
    11.         Math.max();
    12.         Math.min();
    13.         Math.ceil()  上取整
    14.         Math.floor() 下取整
    15.         Math.round()  四舍五入取整
    16.         Math.random()   //    0<=num<1
    17.         1-100
    18.          */
    20.          /* 
    21.          Math.random()*100
    22.              0<=num<99.999
    23.              Math.floor(Math.random()*100)
    24.               0<=num<99;
    25.               Math.floor(Math.random()*100)+1
    26.               1<=num<100;
    27.           */
    28.         var num  = 12.66;
    29.         console.log(Math.ceil(num))
    30.         console.log(Math.floor(num))
    31.         console.log(Math.round(num))
    32.         console.log(Math.random())
    33.     </script>
    34. </body>
    35. </html>