72 lines
1.7 KiB
Plaintext
72 lines
1.7 KiB
Plaintext
|
/**
|
||
|
|
* 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.
|
||
|
|
*
|
||
|
|
* @providesModule equalsIterable
|
||
|
|
* @flow
|
||
|
|
*/
|
||
|
|
'use strict';
|
||
|
|
|
||
|
|
const enumerate = require("./enumerate");
|
||
|
|
/**
|
||
|
|
* Checks if two iterables are equal. A custom areEqual function may be provided
|
||
|
|
* as an optional third argument.
|
||
|
|
*/
|
||
|
|
|
||
|
|
|
||
|
|
function equalsIterable<T>(one: Iterable<T>, two: Iterable<T>, areEqual?: ?(one: T, two: T) => boolean): boolean {
|
||
|
|
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: any): ?number {
|
||
|
|
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<T>(one: T, two: T): boolean {
|
||
|
|
return one === two;
|
||
|
|
}
|
||
|
|
|
||
|
|
module.exports = equalsIterable;
|