/** * Copyright (c) Meta Platforms, Inc. and affiliates. * * This source code is licensed under the MIT license found in the * LICENSE file in the root directory of this source tree. * * @flow * @format */ /** * @return whether or not a @param {function} f is provided natively by calling * `toString` and check if the result includes `[native code]` in it. * * Note that a polyfill can technically fake this behavior but few does it. * Therefore, this is usually good enough for our purpose. */ function isNativeFunction(f: Function): boolean { return typeof f === 'function' && f.toString().indexOf('[native code]') > -1; } /** * @return whether or not the constructor of @param {object} o is an native * function named with @param {string} expectedName. */ function hasNativeConstructor(o: Object, expectedName: string): boolean { const con = Object.getPrototypeOf(o).constructor; return con.name === expectedName && isNativeFunction(con); } module.exports = {isNativeFunction, hasNativeConstructor};