githubmr/facebook-react: The library for web and native user interfaces.

packages/shared/hasBadMapPolyfill.js

26 строк745 B

Dominic Gannaway

Adds experimental fundamental interface (#16049)

20 июл 2019, 00:20

20 июл 2019, 00:202c4d61e

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 * @flow
 */

export let hasBadMapPolyfill;

if (__DEV__) {
  hasBadMapPolyfill = false;
  try {
    const frozenObject = Object.freeze({});
    const testMap = new Map([[frozenObject, null]]);
    const testSet = new Set([frozenObject]);
    // This is necessary for Rollup to not consider these unused.
    // https://github.com/rollup/rollup/issues/1771
    // TODO: we can remove these if Rollup fixes the bug.
    testMap.set(0, 0);
    testSet.add(0);
  } catch (e) {
    // TODO: Consider warning about bad polyfills
    hasBadMapPolyfill = true;
  }
}