JS 加減乘除 尤其是減法精度問題

/**
             * 除法
             * */
            division: function(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) {}
                Math.r1 = Number(arg1.toString().replace(".", ""))
                Math.r2 = Number(arg2.toString().replace(".", ""))
                return (Math.r1 / Math.r2) * Math.pow(10, t2 - t1);
            },
            /**
             * 乘法
             * */
            multiplication: function(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)
            },
            /**
             * 加法
             * */
            addition: function(arg1, arg2) {
                var r1, r2, m;
                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));
                return (arg1 * m + arg2 * m) / m;
            },
            /**
             * 減法
             * */
            subtraction: function(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
                //動態控制精度長度
                n = (r1 >= r2) ? r1 : r2;
                return ((arg1 * m - arg2 * m) / m).toFixed(n);
            }