stringsOnlyObject does typechecking before coercion to string

    this._root.setNativeProps(nativeProps);

  }

  toTypeString(x) {

    switch (typeof x) {

      case "object":

        return x instanceof Date 

          ? x.toISOString() 

          : JSON.stringify(x); // object, null

      case "undefined":

        return "";

      default: // boolean, number, string

        return x.toString();      

    }

  }

  stringsOnlyObject(obj) {

    const strObj = {};

    Object.keys(obj).forEach(x => {

      strObj[x] = this.toTypeString(obj[x]);

    });

    return strObj;

  }

  stringsOnlyObject(obj) {

    const strObj = {};