NaN类型
NaN 即 not a number 当某个计算值结果不为数值类型时就返回为NaN
<body>
<script>
console.log(Number("abc"));
console.log(2/"aaa");
//NaN类型不能与NaN类型比较，即不能和自己比较
console.log(NaN ==NaN);
//比较某个值是否为NaN的方法 两种方法
console.log(Number.isNaN(2/"aaa"));
console.log(Object.is(2/"abc",NaN));
</script>
</body>
Math
<body>
<script>
//获取最大值最小值
console.log(Math.min(2,5,4,99,1,55,88,123));
console.log(Math.max(2,5,4,99,1,55,88,123));
let arr1=[2,5,4,99,1,55,88,123];
console.log(Math.min(arr1)); //结果为NaN，因为不能直接传入数组.
console.log(Math.max.apply(null,arr1));//在数组中去最大最小值的方法
console.log(Math.ceil(5.01));//向上取整
console.log(Math.floor(5.99));//向下取整
console.log((5.654).toFixed(2));//四舍五入
console.log(Math.round(5.56));
</script>
</body>