//加法Number.prototype.add = function (arg) {var r1, r2, m;try { r1 = this.toString().split(".")[1].length } catch (e) { r1 = 0 }try { r2 = arg.toString().split(".")[1].length } catch (e) { r2 = 0 }m = Math.pow(10, Math.max(r1, r2))return (this * m + arg * m) / m}//减法Number.prototype.sub = function (arg) {return this.add(-arg);}//乘法Number.prototype.mul = function (arg) {var m = 0, s1 = this.toString(), s2 = arg.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)}//除法Number.prototype.div = function (arg) {var t1 = 0, t2 = 0, r1, r2;try { t1 = this.toString().split(".")[1].length } catch (e) { }try { t2 = arg.toString().split(".")[1].length } catch (e) { }with (Math) {r1 = Number(this.toString().replace(".", ""))r2 = Number(arg.toString().replace(".", ""))return (r1 / r2) * pow(10, t2 - t1);}}var floatObj = function () {/** 判断obj是否为一个整数*/function isInteger(obj) {return Math.floor(obj) === obj}/** 将一个浮点数转成整数，返回整数和倍数。如 3.14 >> 314，倍数是 100* @param floatNum {number} 小数* @return {object}*   {times:100, num: 314}*/function toInteger(floatNum) {var ret = { times: 1, num: 0 }if (isInteger(floatNum)) {ret.num = floatNumreturn ret}var strfi = floatNum + ''var dotPos = strfi.indexOf('.')var len = strfi.substr(dotPos + 1).lengthvar times = Math.pow(10, len)var intNum = parseInt(floatNum * times + 0.5, 10)ret.times = timesret.num = intNumreturn ret}/** 核心方法，实现加减乘除运算，确保不丢失精度* 思路：把小数放大为整数（乘），进行算术运算，再缩小为小数（除）** @param a {number} 运算数1* @param b {number} 运算数2* @param digits {number} 精度，保留的小数点数，比如 2, 即保留为两位小数* @param op {string} 运算类型，有加减乘除（add/subtract/multiply/divide）**/function operation(a, b, digits, op) {var o1 = toInteger(a)var o2 = toInteger(b)var n1 = o1.numvar n2 = o2.numvar t1 = o1.timesvar t2 = o2.timesvar max = t1 > t2 ? t1 : t2var result = nullswitch (op) {case 'add':if (t1 === t2) { // 两个小数位数相同result = n1 + n2} else if (t1 > t2) { // o1 小数位 大于 o2result = n1 + n2 * (t1 / t2)} else { // o1 小数位 小于 o2result = n1 * (t2 / t1) + n2}return result / maxcase 'subtract':if (t1 === t2) {result = n1 - n2} else if (t1 > t2) {result = n1 - n2 * (t1 / t2)} else {result = n1 * (t2 / t1) - n2}return result / maxcase 'multiply':result = (n1 * n2) / (t1 * t2)return resultcase 'divide':result = (n1 / n2) * (t2 / t1)return result}}// 加减乘除的四个接口function add(a, b, digits) {return operation(a, b, digits, 'add')}function subtract(a, b, digits) {return operation(a, b, digits, 'subtract')}function multiply(a, b, digits) {return operation(a, b, digits, 'multiply')}function divide(a, b, digits) {return operation(a, b, digits, 'divide')}function toFixed(num, s) {try {s = s || (num + '').split(".")[1].length;} catch (e) { }var times = Math.pow(10, s + 1)var des = num * times + 5des = parseInt(des / 10, 10) * 10 / timesreturn des + ''}// exportsreturn {add: add,subtract: subtract,multiply: multiply,divide: divide,toFixed: toFixed}}();// toFixed 修复const abc = floatObj.toFixed(2.1,2)