@magento/peregrine/src/RestApi/Magento2/MulticastCache.js

/**
 * Network requests that have not yet fulfilled, available for sharing with
 * other idempotent and safe M2ApiRequests for the same resource.
 * Resource matching is determined by a string composite [method, path, body].
 *
 * (M2ApiRequests know not to use this cache for create operations, except for
 * singleton create operations like createGuestCart, which have no body.)
 * @module MulticastCache
 */

/**
 * String keyed map of in-flight requests. When a request completes,
 * it should be removed.
 * @private
 */
const inflight = new Map();

/**
 * Reference cache to reduce repetitive requestToKey() calls.
 * @private
 */
const keyCache = new WeakMap();

/**
 *
 * @private
 * @param {M2ApiRequest} req
 * @return string Key for use in inflight cache.
 */
function requestToKey(req) {
    let key = keyCache.get(req);
    if (!key) {
        const { method, body } = req.opts;
        const parts = [method, req.resourceUrl];
        if (body) {
            parts.push(body);
        }
        key = parts.join('|||');
        keyCache.set(req, key);
    }
    return key;
}

/**
 * Returns any inflight request with the same key as the supplied request.
 * May be the same request itself!
 * @param {M2ApiRequest} req The request to match.
 * @return {M2ApiRequest} A request with the same method, body, and resourceUrl..
 */
export function match(req) {
    return inflight.get(requestToKey(req));
}
/**
 * Store a request for potential future multicast.
 * Adds a callback to delete the request when it has settled.
 * @param {M2ApiRequest} req The request to store.
 */
export function store(req) {
    inflight.set(requestToKey(req), req);
}
/**
 * Remove a request from cache if it exists there.
 * @param {M2ApiRequest} req
 */
export function remove(req) {
    if (match(req) === req) {
        inflight.delete(requestToKey(req));
    }
}