funfix-effect
Version:
Sub-package of Funfix defining monadic data types for dealing with laziness and side effects
45 lines • 1.43 kB
JavaScript
/*!
* Copyright (c) 2017-2018 by The Funfix Project Developers.
* Some rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Reusable empty `IteratorLike` reference.
*
* @hidden
*/
export const emptyIteratorRef = { next: () => ({ done: true }) };
/**
* Given an array or an `Iterable`, returns a simple iterator type
* that we can use to traverse the given list lazily.
*
* @hidden
*/
export function iteratorOf(list) {
if (!list)
return emptyIteratorRef;
if (Object.prototype.toString.call(list) !== "[object Array]")
return list[Symbol.iterator]();
const array = list;
if (array.length === 0)
return emptyIteratorRef;
let cursor = 0;
const next = () => {
const value = array[cursor++];
const done = cursor >= array.length;
return { done, value };
};
return { next };
}
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