javascript两个数值简单运算精度修正函数

之前发在csdn的javascript版
------------------------------
/*
* 数值简单运算精度修正函数
* m 数值1(number)
* n 数值2(number)
* op 操作符(string)
*/
function fixMath(m, n, op) {
var a = (m+"");
var b = (n+"");
var x = 1;
var y = 1;
var c = 1;
if(a.indexOf(".")>0) {
x = Math.pow(10, a.length - a.indexOf(".") - 1);
}
if(b.indexOf(".")>0) {
y = Math.pow(10, b.length - b.indexOf(".") - 1);
}
switch(op)
{
case '+':
case '-':
c = Math.max(x,y);
m = Math.round(m*c);
n = Math.round(n*c);
break;
case '*':
c = x*y
m = Math.round(m*x);
n = Math.round(n*y);
break;
case '/':
c = Math.max(x,y);
m = Math.round(m*c);
n = Math.round(n*c);
c = 1;
break;
}
return eval("("+m+op+n+")/"+c);
}

用法如下:
-----------------------
fixMath(2.3, 1.9, '*')
fixMath(1.98, 1.9, '-')
fixMath(83.50, 74.15, '-')