Function objectToString

static/plugins/pdfmake/pdfmake.js:71953–71955

(o)

function isError(e) {
  return isObject(e) &&
      (objectToString(e) === '[object Error]' || e instanceof Error);
}
exports.isError = isError;
exports.types.isNativeError = isError;

function isFunction(arg) {