Math扩展

<script>
    console.log(Math.trunc(4.9));
    console.log(Math.trunc(-4.9));
    //Math.sign方法用来判断一个正数、负数、零。对于非数值，会先将其转化成数值
    console.log(Math.sign(10));//+1
    console.log(Math.sign(-10));//-1
    console.log(Math.sign(0));  //0
    console.log(Math.sign(-0));//-0
    console.log(Math.sinh("hello"));//NaN
    //Math.cbrt()立方根
    console.log(Math.cbrt(8));//2
</script>