39 lines
1.3 KiB
JavaScript
39 lines
1.3 KiB
JavaScript
'use strict';
|
|
|
|
/**
|
|
* Copyright (c) 2013-present, Facebook, Inc.
|
|
*
|
|
* This source code is licensed under the MIT license found in the
|
|
* LICENSE file in the root directory of this source tree.
|
|
*
|
|
* @preventMunge
|
|
*
|
|
*/
|
|
|
|
/**
|
|
* Checks whether a collection name (e.g. "Map" or "Set") has a native polyfill
|
|
* that is safe to be used.
|
|
*/
|
|
function shouldPolyfillES6Collection(collectionName) {
|
|
var Collection = global[collectionName];
|
|
if (Collection == null) {
|
|
return true;
|
|
}
|
|
|
|
// The iterator protocol depends on `Symbol.iterator`. If a collection is
|
|
// implemented, but `Symbol` is not, it's going to break iteration because
|
|
// we'll be using custom "@@iterator" instead, which is not implemented on
|
|
// native collections.
|
|
if (typeof global.Symbol !== 'function') {
|
|
return true;
|
|
}
|
|
|
|
var proto = Collection.prototype;
|
|
|
|
// These checks are adapted from es6-shim: https://fburl.com/34437854
|
|
// NOTE: `isCallableWithoutNew` and `!supportsSubclassing` are not checked
|
|
// because they make debugging with "break on exceptions" difficult.
|
|
return Collection == null || typeof Collection !== 'function' || typeof proto.clear !== 'function' || new Collection().size !== 0 || typeof proto.keys !== 'function' || typeof proto.forEach !== 'function';
|
|
}
|
|
|
|
module.exports = shouldPolyfillES6Collection; |