【ES】笔记-数值扩展

文章来源地址https://uudwc.com/A/qRyve
数值扩展

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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>数值扩展</title>
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    <script>
       // 0.Number.EPSION 是javaScript 表示的最小精度
       //EPSILON 属性的值接近于2.22044604925031308088472633361816e-16
        function equal(a,b){
            if(Math.abs(a-b)<Number.EPSILON){
                return true;
            }else{
                return false;
            }
        }
        console.log(0.1+0.2===0.3); //打印false
        console.log(equal(0.1+0.2,0.3)); //打印true

        //1. 二进制和八进制
        let b=0b1010;
        let o=0o777;
        console.log(b); //打印10
        console.log(o); //打印511

        let d=100;
        let x=0xff;
        console.log(d); //打印100
        console.log(x); //打印255

        //2.Number.isInteger 判断一个数是否为有限数
        console.log(Number.isFinite(100)); //打印true
        console.log(Number.isFinite(100/0)); //打印false
        console.log(Number.isFinite(Infinity)); //打印false

        //3.Number.isNaN 检测一个数值是否为NaN
        console.log(Number.isNaN(123)); //打印false

        //4. Number.parseInt Number.parseFloat 字符串转整数
        console.log(Number.parseInt(5)); //打印5
        console.log(Number.parseFloat ('3.1415926神奇')); //打印3.1415926

        //5.Number.isInteger 判断一个数是否为整数
        console.log(Number.isInteger(5));   //打印true
        console.log(Number.isInteger(2.5)); //打印false

        //6.Math.trunc 将数字的小数部分抹掉
        console.log(Math.trunc(3.5)) //打印3

        //7.Math.sign 判断一个数到底为正数 负数 还是零
        console.log(Math.sign(100)); //打印1
        console.log(Math.sign(-20)); //打印-1
        console.log(Math.sign(0));   //打印0



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