js 现给数字加三位一逗号间隔的种方法

 思想：不论是几位加逗号，首先变成字符串，获取长度，除以位数，得到整数a，和余数，接下来就是循环，字符串截取对应的加‘，’，其实还有要熟练掌握数组和字符串的各种方法，对应这周小的算法还是可以很快实现的，希望对你有帮助！

    function getResult(num) {
        if (num && num !== null) {
          var num = num.toString();
          var length = num.length;
          var arr = num.split('');
          var remainder = length % 3; //取余数
          var integer = parseInt(length / 3); //取整数
          var frontNum = '';
          for (var i = 0; i < integer; i++) {
            frontNum = frontNum + num.substr(i * 3, 3) + ',';
          }
          if (remainder > 0) {
            var remNum = num.substr(integer * 3, remainder);
            return frontNum + remNum;
          } else {
            return frontNum.substring(0, frontNum.length - 1);
          }

        }
      }
      var num = 12345678789098;
      var result = getResult(num);
      var num1 = 123456;
      var result1 = getResult(num1);
      console.log(result)
      console.log(result1)