Javascript 浮点数精确计算

来源：互联网发布：php开发app接口源码编辑：程序博客网时间：2024/05/17 02:11

浮点数计算精度问题是javascript自身存在的问题。

比较经典的例子为2.0-1.1, 计算的结果为0.8999999999999999。

精确计算的基本思路是将其全部转换为整数后计算，整数计算不存在误差，然后再除以之前乘的数。

如下代码1为测试html，引用的js见代码2。也可以下载附件，附件中已经都包含。

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>浮点数精确计算测试</title><script type="text/javascript" src="js/FloatCumulateV1.js"></script><script type="text/javascript">    window.onload = function(){    document.getElementById("1").innerHTML = (0.01/0.1) ;    document.getElementById("2").innerHTML = (Number(0.01).div(Number(0.1))) ;        document.getElementById("3").innerHTML = (1.5*0.1) ;    document.getElementById("4").innerHTML = (Number(1.5).mul(Number(0.1))) ;        document.getElementById("5").innerHTML = (0.09999999+0.00000001) ;    document.getElementById("6").innerHTML = (Number(0.09999999).add(Number(0.00000001))) ;        document.getElementById("7").innerHTML = (2.0-1.1) ;    document.getElementById("8").innerHTML = (Number(2.0).sub(Number(1.1))) ;        document.getElementById("9").innerHTML = (Number(10).div(Number(0.1))) ;    document.getElementById("10").innerHTML = (Number(10).mul(Number(0.1))) ;    document.getElementById("11").innerHTML = (Number(10).add(Number(0.2))) ;    document.getElementById("12").innerHTML = (Number(10).sub(Number(1.1))) ;        }</script></head><body><h1>浮点数精确计算测试</h1><p>普通js除法计算: 0.01/0.1 = <label id="1"> </label></p><p>当前js除法计算: 0.01/0.1 = <label id="2"> </label></p><p>普通js乘法计算: 1.5*0.1 = <label id="3"> </label></p><p>当前js乘法计算: 1.5*0.1 = <label id="4"> </label></p><p>普通js加法计算: 0.09999999+0.00000001 = <label id="5"> </label></p><p>当前js加法计算: 0.09999999+0.00000001 = <label id="6"> </label></p><p>普通js减法计算: 2.0-1.1 = <label id="7"> </label></p><p>当前js减法计算: 2.0-1.1 = <label id="8"> </label></p><p>当前js除法计算(不带小数，测试Exception的分支): 10/0.1 = <label id="9"> </label></p><p>当前js乘法计算(不带小数，测试Exception的分支): 10*0.1 = <label id="10"> </label></p><p>当前js加法计算(不带小数，测试Exception的分支): 10+0.2 = <label id="11"> </label></p><p>当前js减法计算(不带小数，测试Exception的分支): 10-1.1= <label id="12"> </label></p></body></html>

此html运行结果:

浮点数精确计算测试普通js除法计算: 0.01/0.1 = 0.09999999999999999当前js除法计算: 0.01/0.1 = 0.1普通js乘法计算: 1.5*0.1 = 0.15000000000000002当前js乘法计算: 1.5*0.1 = 0.15普通js加法计算: 0.09999999+0.00000001 = 0.09999999999999999当前js加法计算: 0.09999999+0.00000001 = 0.1普通js减法计算: 2.0-1.1 = 0.8999999999999999当前js减法计算: 2.0-1.1 = 0.9当前js除法计算(不带小数，测试Exception的分支): 10/0.1 = 100当前js乘法计算(不带小数，测试Exception的分支): 10*0.1 = 1当前js加法计算(不带小数，测试Exception的分支): 10+0.2 = 10.2当前js减法计算(不带小数，测试Exception的分支): 10-1.1= 8.9

计算的JS

function accDiv(arg1, arg2){var tmp1 = 0;var tmp2 = 0;var result1 = 0;var result2 = 0;    //获取异常的目的是防止存在整数的情况。try {tmp1 = arg1.toString().split(".")[1].length;} catch(e) {tmp1 = 0;}try {tmp2 = arg2.toString().split(".")[1].length;} catch(e) {tmp2 = 0;}result1 = Number(arg1.toString().replace(".", ""));result2 = Number(arg2.toString().replace(".", ""));return (result1 / result2) * Math.pow(10, tmp2 - tmp1);}Number.prototype.div = function(arg) {return accDiv(this, arg);}function accMul(arg1, arg2) {var tmp1 = 0;var tmp2 = 0;var result1 = 0;var result2 = 0;try {tmp1 = arg1.toString().split(".")[1].length;} catch (e) {        tmp1 = 0;}try {tmp2 = arg2.toString().split(".")[1].length;} catch (e) {tmp2 = 0;}result1 = Number(arg1.toString().replace(".", ""));result2 = Number(arg2.toString().replace(".", ""));return (result1 * result2) / Math.pow(10, tmp1 + tmp2);}Number.prototype.mul = function(arg) {return accMul(this, arg);}function accAdd(arg1, arg2) {var tmp1 = 0;var tmp2 = 0;var tmp = 0;var result1 = 0;var result2 = 0;try {tmp1 = arg1.toString().split(".")[1].length;} catch (e) {tmp1 = 0;}try {tmp2 = arg2.toString().split(".")[1].length;} catch (e) {tmp2 = 0;}//arg1 + arg2 = ( result1/Math.pow(10,tmp1) ) + ( result2/Math.pow(10,tmp2) )//1.5+0.02 = 15/10 + 2/100//1.5+0.02 = 1.5*100/100 + 2*100/100tmp = Math.max(tmp1, tmp2);    /**     * 解决 319500-301418.09     *        38890.91+116672.73+38890.91     *        2.0-1.1     * 对于javascript计算，直接*10或者*100也会出现精度错误，因此采用字符串的方式解决     */result1 = arg1;result2 = arg2;var tmpStr = '';if (tmp>0){tmpStr = arg1.toString().replace('.','');for (var i=0;i<tmp-tmp1;i++){tmpStr += '0';}result1 = Number(tmpStr);tmpStr = arg2.toString().replace('.','');for (var i=0;i<tmp-tmp2;i++){tmpStr += '0';}result2 = Number(tmpStr);}//return (arg1 * Math.pow(10, tmp) + arg2 * Math.pow(10, tmp)) / Math.pow(10, tmp);return (result1 + result2) / Math.pow(10, tmp);}Number.prototype.add = function(arg) {return accAdd(this, arg);}//减法的思路可以参照加法的思路。function accSub(arg1, arg2) {var tmp1 = 0;var tmp2 = 0;var tmp = 0;var result1 = 0;var result2 = 0;try {tmp1 = arg1.toString().split(".")[1].length;} catch (e) {tmp1 = 0;}try {tmp2 = arg2.toString().split(".")[1].length;} catch (e) {tmp2 = 0;}tmp = Math.max(tmp1, tmp2);    /**     * 解决 319500-301418.09     *        38890.91+116672.73+38890.91     *        2.0-1.1     * 对于javascript计算，直接*10或者*100也会出现精度错误，因此采用字符串的方式解决     */result1 = arg1;result2 = arg2;var tmpStr = '';if (tmp>0){tmpStr = arg1.toString().replace('.','');for (var i=0;i<tmp-tmp1;i++){tmpStr += '0';}result1 = Number(tmpStr);tmpStr = arg2.toString().replace('.','');for (var i=0;i<tmp-tmp2;i++){tmpStr += '0';}result2 = Number(tmpStr);}//return (arg1 * Math.pow(10, tmp) - arg2 * Math.pow(10, tmp)) / Math.pow(10, tmp);return (result1 - result2) / Math.pow(10, tmp);}Number.prototype.sub = function(arg) {return accSub(this, arg);}

NewProject.zip (2 KB)
下载次数: 0

阅读全文

0 0