weex中的运算保证精度

//精准加法函数

exports.add = function(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;

  }

  m = Math.pow(10, Math.max(r1, r2));

  c = Math.abs(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;

},


//精准减法函数

exports.sub = 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)); //last modify by deeka //动态控制精度长度


  return (exports.mul(arg1, m) - exports.mul(arg2, m)) / m;

},


//精准乘法函数

exports.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);

},


//精准除法函数

exports.div = 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) {}

  r1 = Number(arg1.toString().replace(".", ""));

  r2 = Number(arg2.toString().replace(".", ""));


  return mul(r1 / r2, Math.pow(10, t2 - t1));

},

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