js 加减乘除以及四舍五入新写法-白红宇

js 加减乘除以及四舍五入新写法

阅读量：5132 次

发布时间：2019-06-13

本文共 3570 字，大约阅读时间需要 11 分钟。

1 四舍五入

eg: (1.23).round() = 1.2

(1.2456).round(3) = 1.246

Number.prototype.round = function (count) {    var res = 0;    var val = this.toString();    var num = parseInt(count || 2);    var dataArr = val.split('.');    var arr1 = dataArr[0] || "";    var arr2 = dataArr[1] || "";    var newArr2 = arr2;    if (arr2.length > num) {      var lastNum = arr2.substring(num, num + 1);      if (parseInt(lastNum) >= 5) {        newArr2 = parseInt(newArr2.substring(0, num)) + 1;        newArr2 = newArr2.toString();        if(newArr2.length
     
       num) {            arr1 = (parseInt(arr1) + 1).toString();            newArr2 = newArr2.substring(1, 3);        }      }    }    val = parseFloat(arr1 + '.' + newArr2);    res = parseFloat(val.toFixed(num));    return res;  }

2 加减乘除

eg: (1).plus(2) = 3

if (!Number.prototype.plus) { //'+'    Number.prototype.plus = function (addend) {        var arg1 = this,            arg2 = addend;        var r1,            r2,            m,            num1,            num2;        try {            r1 = arg1.toString().split(".")[1].length;        } catch (e) {            r1 = 0        }        try {            r2 = arg2.toString().split(".")[1].length;        } catch (e) {            r2 = 0        }        m = Math.pow(10, Math.max(r1, r2));        num1 = r1 == 0 ? parseInt(arg1 * m) : (parseInt(`${arg1.toString().replace('.', '')}`) * m / (Math.pow(10, r1)));        num2 = r2 == 0 ? parseInt(arg2 * m) : (parseInt(`${arg2.toString().replace('.', '')}`) * m / (Math.pow(10, r2)));        return (num1 + num2) / m;    }}if (!Number.prototype.minus) { //'-'    Number.prototype.minus = function (Subtraction) {        var arg1 = this,            arg2 = Subtraction;        var r1,            r2,            m,            n,            num1,            num2;        try {            r1 = arg1.toString().split(".")[1].length        } catch (e) {            r1 = 0        }        try {            r2 = arg2.toString().split(".")[1].length        } catch (e) {            r2 = 0        }        m = Math.pow(10, Math.max(r1, r2));        n = (r1 >= r2) ? r1 : r2;        num1 = r1 == 0 ? parseInt(arg1 * m) : (parseInt(`${arg1.toString().replace('.', '')}`) * m / (Math.pow(10, r1)));        num2 = r2 == 0 ? parseInt(arg2 * m) : (parseInt(`${arg2.toString().replace('.', '')}`) * m / (Math.pow(10, r2)));        return parseFloat(((num1 - num2) / m).toFixed(n));    }}if (!Number.prototype.multiply) { //'*'    Number.prototype.multiply = function (multiple) {        var arg1 = this,            arg2 = multiple;        var m = 0,            s1 = arg1.toString(),            s2 = arg2.toString();        try {            m += s1.split(".")[1].length        } catch (e) { }        try {            m += s2.split(".")[1].length        } catch (e) { }        return Number(s1.replace(".", "")) * Number(s2.replace(".", "")) / Math.pow(10, m)    }    if (!Number.prototype.devide) { //'/'        Number.prototype.devide = function (divisor) {            var arg1 = this,                arg2 = divisor;            var t1 = 0,                t2 = 0,                r1,                r2;            try {                t1 = arg1.toString().split(".")[1].length            } catch (e) { }            try {                t2 = arg2.toString().split(".")[1].length            } catch (e) { }            r1 = Number(arg1.toString().replace(".", ""))            r2 = Number(arg2.toString().replace(".", ""))            return (r1 / r2).multiply(Math.pow(10, t2 - t1));        }    }}

转载于:https://www.cnblogs.com/zxhome/p/10342313.html

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