simple, ugly and working (should probably be a class)

cache-promise-returns.mjs

/*
 * cache module for promise returns
 *
 * @author Nabil Redmann <repo+gist@bananaacid.de>
 * @license ISC
 *
 * USE:
 *   cache.setTTL(10*1000); // optional
 *
 *   let [ret1, ret2, ret3] = await cache.create( 
 *       async() => await Promise.all([
 *           async a => 1
 *       ], false)
 *   );
 *
 *   cache.init();   // to reset
 */
let cacheOpts = {
    ttl: 10*1000, // secs

    time: null,
    data: [],
};

let cache = {...cacheOpts,
    ...{
        init: (ttl) => cache = {...cache, ...cacheOpts, ...(ttl !== undefined ? {ttl} : {})},
        setTTL: ttl => cache.ttl = ttl,

        create: async (retProm, enforce) => {
            if (enforce || (cache.time <= +(new Date))) {
               cache.time = +(new Date) + cache.ttl;

               // console.log('CACHE refresh', {ttl: cache.ttl, next_time: cache.time, now:  +(new Date)});

               cache.data = await retProm();
            }
           
            return cache.data;
        },

        isValid: _ => (cache.time > +(new Date)),
        get: pos => cache.data[pos],
        getAll: _ => cache.data,
        has: pos => !!cache.data[pos]
    }
};