js浮点数的计算

        total=total+price;
	total=total.toString();
	if(total.lastIndexOf(‘.‘)==-1){
	  total=total;
	}else{
	  total=total.substr(0,total.lastIndexOf(‘.‘)+3);
	}
	total=parseFloat(total);
//因为浮点数总会出现类似这种0.3+01=0.40000000001之类的错误,所以我直接总是取两位小数,去掉后面的一大串@%*G$%#FF&^$$&%
//看起来很简单,正是因为处理方式太多简单粗暴,错误很快发现了 类似0.06+0.01=0.699999999,业务里是price,可见这种显示错误是很难让人容忍的,为什么0.06+0.01不能得到0.07,
//若是购买多个累加时会变成误差多少?　

//加法
function f_add(arg1,arg2){
        var r1, r2, m, c;
        try {
            r1 = arg1.toString().split(".")[1].length;
        }
        catch (e) {
            r1 = 0;
        }
        try {
            r2 = arg2.toString().split(".")[1].length;
        }
        catch (e) {
            r2 = 0;
        }
        c = Math.abs(r1 - r2);
        m = Math.pow(10, Math.max(r1, r2));
        if (c > 0) {
            var cm = Math.pow(10, c);
            if (r1 > r2) {
               arg1 = Number(arg1.toString().replace(".", ""));
               arg2 = Number(arg2.toString().replace(".", "")) * cm;
            } else {
               arg1 = Number(arg1.toString().replace(".", "")) * cm;
               arg2 = Number(arg2.toString().replace(".", ""));
            }
        } else {
            arg1 = Number(arg1.toString().replace(".", ""));
            arg2 = Number(arg2.toString().replace(".", ""));
        }
        return (arg1 + arg2) / m;
}

//减法
function f_sub(arg1,arg2){
        var r1, r2, m, n;
        try {
           r1 = arg1.toString().split(".")[1].length;
        }
        catch (e) {
            r1 = 0;
        }
        try {
            r2 = arg2.toString().split(".")[1].length;
        }
        catch (e) {
            r2 = 0;
        }
        m = Math.pow(10, Math.max(r1, r2)); //last modify by deeka //动态控制精度长度
        n = (r1 >= r2) ? r1 : r2;
        return ((arg1 * m - arg2 * m) / m).toFixed(n);

}

//乘法
function f_times(arg1, arg2) {
    var m = 0, s1 = arg1.toString(), s2 = arg2.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
function f_slash(arg1, arg2) {

    var t1 = 0, t2 = 0, r1, r2;
    try {
        t1 = arg1.toString().split(".")[1].length;
    }
    catch (e) {
    }
    try {
        t2 = arg2.toString().split(".")[1].length;
    }
    catch (e) {
    }
    with (Math) {
        r1 = Number(arg1.toString().replace(".", ""));
        r2 = Number(arg2.toString().replace(".", ""));
        return (r1 / r2) * pow(10, t2 - t1);
    }
}