docs: function ltrim(str, targetStr) {
      var retStr = "";
      var regStr;
  
      if (typeof str != "string") {
          return retStr;
      }
  
      if (typeof targetStr != "string" || !targetStr) {
          targetStr = "\\s";
      }
  
      regStr = "^" + targetStr + "*(.*?)";
      regStr = new RegExp(regStr);
  
      str = str.replace(regStr, "$1");
      return str;
  }