如何让json对象的键值是变量

 var table = document.getElementById("tableId");
      var tbody = table.getElementsByTagName("tbody")[0];
      var trs = tbody.getElementsByTagName("tr");
      var obj = {};
      var trsArr = [];
      for (i = 0;i < trs.length;i++){
        var tds  = trs[i].getElementsByTagName("td");
        for (var j = 0;j < tds.length;j++){
            var ss = tds[j].childNodes[0].value;
            var ss1 = tds[j].childNodes[0].name;

            obj[ss1] = ss;//{ss1:ss}这样写的话ss1是字符串“ss1”


        }
        trsArr.push(obj);


      }