Math 是数学函数，但又属于对象数据类型 typeof Math => ‘object’
console.dir(Math) 查看Math的所有函数方法。
1，Math.abs() 获取绝对值
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">Math.abs(-12) = 12</pre>
2，Math.ceil() and Math.floor() 向上取整和向下取整
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;"> console.log(Math.ceil(12.03));//13
console.log(Math.ceil(12.92));//13
console.log(Math.floor(12.3));//12
console.log(Math.floor(12.9));//12</pre>
3，Math.round() 四舍五入
注意：正数时，包含5是向上取整，负数时包含5是向下取整。
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">1、Math.round(-16.3) = -16
2、Math.round(-16.5) = -16
3、Math.round(-16.51) = -17</pre>
4，Math.random() 取[0,1)的随机小数
案例1：获取[0,10]的随机整数
console.log(parseInt(Math.random()*10));//未包含10
console.log(parseInt(Math.random()*10+1));//包含10
案例2：获取[n,m]之间的随机整数
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">Math.round(Math.random()*(m-n)+n)</pre>
5，Math.max() and Max.min() 获取一组数据中的最大值和最小值
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">console.log(Math.max(10,1,9,100,200,45,78));
console.log(Math.min(10,1,9,100,200,45,78));</pre>
6，Math.PI 获取圆周率π 的值
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">console.log(Math.PI);</pre>
7，Math.pow() and Math.sqrt()
Math.pow()获取一个值的多少次幂
Math.sqrt()对数值开方
<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">1.Math.pow(10，2) = 100; 2.Math.sqrt(100) = 10;</pre>
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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">//例子:自己定义一个对象,实现系统的max的方法
function Mymax() { //添加了一个方法
this.getMax = function () { //假设这个数是最大值
var max = arguments[0]; for (var i = 0; i < arguments.length; i++) { if (max < arguments[i]) {
max = arguments[i];
}
} return max;
};
} // 实例对象
var my = new Mymax();
console.log(my.getMax(9, 5, 6, 32));
console.log(Math.max(9, 5, 6, 32));</pre>
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