js加减乘除封装

Math.add = 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;}//减法Math.sub = 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));  //动态控制精度长度  n = (r1 >= r2) ? r1 : r2;  return ((arg1 * m - arg2 * m) / m).toFixed(n);}//乘法Math.mul = 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);}//除法Math.div = function (arg1, arg2) {  if (!arg1)return '';  if (!arg2)return '';  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) {  }  r1 = Number(arg1.toString().replace(".", ""));  r2 = Number(arg2.toString().replace(".", ""));  return (r1 / r2) * Math.pow(10, t2 - t1);}