javascript 计算

javascript在计算的时候，会产生精度的变化，导致计算的结果并非我们想要得到的值，如下面的代码，实际得到的值，其实不是28.21

var a = "28.22";
var b = "0.01";
var fa = parseFloat(CardBal);
var fb = parseFloat(CancelDepAmt);
var result = fa-fb;

如果通过下面的方法，就能够避免这种情况

function Sub_FloatNumberString(val1,val2)
{
var splitChar = ".";
var sp_val1 = val1.split(splitChar);
var sp_val2 = val2.split(splitChar);
var val1_point;
var val2_point;
if (sp_val1.length==1&&sp_val2.length==1)
{
    return val1 - val2;
}
var more = 0;
if (sp_val1.length == 2 && sp_val2.length == 2)
{
    val1_point = sp_val1[1].length;
    val2_point = sp_val2[1].length;
    more = Math.max(val1_point, val2_point);
}
else if (sp_val1.length > sp_val2.length)
{
    more = sp_val1[1].length;
}
else
{
    more = sp_val2[1].length;
}
var val1Int = parseFloat(val1) * Math.pow(10, more);
var val2Int = parseFloat(val2) * Math.pow(10, more);
var sub = val1Int - val2Int;
return sub / Math.pow(10, more);
}