SOURCE

//返回拼好json格式的字符串
function toArray(str)
{
  var list = str.split(",");
  var myStr = "{";
  for(var i=0;i<list.length;i++)
  {
    try{
      var keys = list[i].split("=");
      var key = Trim(keys[0]); 
      var value= Trim(keys[1]);
      if(i>0)
      {
        myStr += ",";
      }
      myStr += "\""+key+"\":\""+value+"\"";
    }catch(e)
    {
      continue;
    }
  }
  myStr += "}";
  return myStr;
}
//替换掉字符串中头尾的空格
function Trim(str){  
    return str.replace(/(^\s*)|(\s*$)/g, "");  
}

function toJson(str)
{
	console.log(eval("("+toArray(str)+")"));
}

<script type="text/javascript">
        toJson("{pk_group=0001Z310000000000BLW, vdef20=null, cinprostuffid=1001A11000000005T1S9, ipricetype=2, modifier=null, ccosttypeid=null, cperiod=2019-08, cmeasdocid=0001Z0100000000000XK, dbusinessdate=2019-08-03 18:54:18, pk_org=0001Z310000000002YIQ, modifiedtime=null, ccostcenterid=1001Z31000000000IGCX, vnote=null, creator=1001Z3100000000004D6, isourcetype=1, vdef10=null, vdef11=null, vdef8=null, vdef7=null, ccostobjectid=1001A31000000001METF, vdef9=null, vdef4=null, vdef3=null, vdef6=N, vdef5=null, vdef2=null, vdef1=null, vbillcode=CMMT2019080300024460, vdef16=null, vdef17=null, vdef18=null, creationtime=2019-08-03 18:54:23, pk_org_v=0001Z310000000002YIP, vdef19=null, vdef12=null, vdef13=null, vdef14=null, ts=2019-08-03 18:54:23, vdef15=null}")
</script>