immutable-js/src/util/is.js

Immutable types in JavaScript

/**
 *  Copyright (c) 2015, Jan Biasi.
 *  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.
 */

export function arrayLike(value) {
    return !!(value && typeof value.length === 'number');
}

export function nullOrUndefined(value) {
    return !!(value === null || value === undefined);
}

/**
 * An extension of the "same-value" algorithm as [described for use by ES6 Map
 * and Set](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map#Key_equality)
 *
 * NaN is considered the same as NaN, however -0 and 0 are considered the same
 * value, which is different from the algorithm described by
 * [`Object.is`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is).
 *
 * This is extended further to allow Objects to describe the values they
 * represent, by way of `valueOf` or `equals` (and `hashCode`).
 *
 * Note: because of this extension, the key equality of Immutable.Map and the
 * value equality of Immutable.Set will differ from ES6 Map and Set.
 *
 */
export function equal(valueA, valueB) {
    if (valueA === valueB || (valueA !== valueA && valueB !== valueB)) {
        return true;
    }
    if (!valueA || !valueB) {
        return false;
    }
    if (typeof valueA.valueOf === 'function' &&
    typeof valueB.valueOf === 'function') {
        valueA = valueA.valueOf();
        valueB = valueB.valueOf();
        if (valueA === valueB || (valueA !== valueA && valueB !== valueB)) {
            return true;
        }
        if (!valueA || !valueB) {
            return false;
        }
    }
    if (typeof valueA.equals === 'function' &&
    typeof valueB.equals === 'function' &&
    valueA.equals(valueB)) {
        return true;
    }
    return false;
}