js计算误差修正代码（真实版）
/*乘法操作
* 1.返回精确的两数相乘的结果，解决了精度的问题
* 2.用此方法返回的结果再调用toFixed方法不会出错
*/
function mulFuncion(num1, num2) {
var totalDigits = 0;
num1 = num1.toString();
num2 = num2.toString();
var numArr1 = num1.split('.');
var numArr2 = num2.split('.');
try { totalDigits += numArr1[1].length; } catch (e) { }
try { totalDigits += numArr2[1].length; } catch (e) { }
var number = num1.replace('.', '') * num2.replace('.', '');
return number / Math.pow(10, totalDigits);
}
/*除法操作
* 1. 返回精确的两数相除的结果，解决了精度的问题
* 2. 用此方法返回的结果再调用toFixed方法不会出错
*/
function divFuncion(num1, num2) {
var decimal1 = 0, decimal2 = 0, decimal1, decimal2;
try { decimal1 = num1.toString().split(".")[1].length } catch (e) { }
try { decimal2 = num2.toString().split(".")[1].length } catch (e) { }
with (Math) {
decimal1 = Number(num1.toString().replace(".", ""))
decimal2 = Number(num2.toString().replace(".", ""))
return (decimal1 / decimal2) * pow(10, decimal2 - decimal1);
}
}
/*加法操作
* 1. 返回精确的两数相加的结果，解决了精度的问题
* 2. 用此方法返回的结果再调用toFixed方法不会出错
*/
function addFuncion(num1, num2) {
var decimal1, decimal2, multiple;
try { decimal1 = num1.toString().split(".")[1].length } catch (e) { decimal1 = 0 }
try { decimal2 = num2.toString().split(".")[1].length } catch (e) { decimal2 = 0 }
multiple = Math.pow(10, Math.max(decimal1, decimal2))
return (num1 * multiple + num2 * multiple) / multiple;
}
/*减法操作
* 1. 返回精确的两数相减的结果，解决了精度的问题
* 2. 用此方法返回的结果再调用toFixed方法不会出错
*/
function subFuncion(num1, num2) {
var decimal1, decimal2, multiple, maxDecimal;
try { decimal1 = num1.toString().split(".")[1].length } catch (e) { decimal1 = 0 }
try { decimal2 = num2.toString().split(".")[1].length } catch (e) { decimal2 = 0 }
multiple = Math.pow(10, Math.max(decimal1, decimal2));
//动态控制精度长度
maxDecimal = (decimal1 >= decimal2) ? decimal1 : decimal2;
return ((num1 * multiple - num2 * multiple) / multiple).toFixed(maxDecimal);
}
/*将number四舍五入到decimals位
* 1.number可以是数字或数字字符串（计算得来的如262.2000000000003这样的数字也行）,不支持科学计数法的数字
* 2.decimals可以是数字或数字字符串（0和负数也行）
*/
function format_number(number, decimals) {
if (isNaN(number)) { return 0 };
if (number == '') { return 0 };
decimals = parseInt(decimals);
number = parseFloat(number);
alert(number);
var numStr = new String(number);
var numArr = numStr.split('.');
var whole = parseFloat(numArr[0]);
var result = '';
// 如果decimals是正数
if (decimals > 0) {
if (numArr.length > 1) {
var dec = new String(numArr[1]);
dec = String(parseFloat(dec) / Math.pow(10, (dec.length - decimals)));
dec = String(whole + Math.round(parseFloat(dec)) / Math.pow(10, decimals));
var dot = dec.indexOf('.');
if (dot == -1) {
dec += '.';
dot = dec.indexOf('.');
}
var totalLength = dot + decimals;
while (dec.length <= totalLength) {
dec += '0';
}
result = dec;
} else {
var dot;
var dec = new String(whole);
dec += '.';
dot = dec.indexOf('.');
while (dec.length <= dot + decimals) { dec += '0'; }
result = dec;
}
}
// 如果decimals是负数
else {
decimals = 0 - decimals;
if (numArr[0].length - decimals - 1 < 0) {
result = "0";
} else {
var leftLength = numArr[0].toString().length - decimals;
whole = parseInt(numStr.substring(0, leftLength));
var dec = parseFloat(numStr.substr(leftLength, numStr.length));
dec = Math.round(dec / Math.pow(10, decimals));
dec = String(whole + dec);
while (dec.length < numArr[0].length) {
dec += "0";
}
result = dec;
}
}
return result;
}