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Diffstat (limited to 'node_modules/fbjs/lib/equalsIterable.js')
-rw-r--r-- | node_modules/fbjs/lib/equalsIterable.js | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/node_modules/fbjs/lib/equalsIterable.js b/node_modules/fbjs/lib/equalsIterable.js new file mode 100644 index 000000000..e17c85c97 --- /dev/null +++ b/node_modules/fbjs/lib/equalsIterable.js @@ -0,0 +1,66 @@ +/** + * Copyright (c) 2013-present, Facebook, Inc. + * All rights reserved. + * + * This source code is licensed under the BSD-style license found in the + * LICENSE file in the root directory of this source tree. An additional grant + * of patent rights can be found in the PATENTS file in the same directory. + * + * + */ + +'use strict'; + +var enumerate = require('./enumerate'); + +/** + * Checks if two iterables are equal. A custom areEqual function may be provided + * as an optional third argument. + */ +function equalsIterable(one, two, areEqual) { + if (one === two) { + return true; + } + + // We might be able to short circuit by using the size or length fields. + var oneSize = maybeGetSize(one); + var twoSize = maybeGetSize(two); + if (oneSize != null && twoSize != null && oneSize !== twoSize) { + return false; + } + + // Otherwise use the iterators to check equality. Here we cannot use for-of + // because we need to advance the iterators at the same time. + var oneIterator = enumerate(one); + var oneItem = oneIterator.next(); + var twoIterator = enumerate(two); + var twoItem = twoIterator.next(); + var safeAreEqual = areEqual || referenceEquality; + while (!(oneItem.done || twoItem.done)) { + if (!safeAreEqual(oneItem.value, twoItem.value)) { + return false; + } + oneItem = oneIterator.next(); + twoItem = twoIterator.next(); + } + return oneItem.done === twoItem.done; +} + +function maybeGetSize(o) { + if (o == null) { + return null; + } + if (typeof o.size === 'number') { + return o.size; + } + if (typeof o.length === 'number') { + return o.length; + } + return null; +} + +function referenceEquality(one, two) { + return one === two; +} + +module.exports = equalsIterable;
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