multiApiCall.js

/* An incredibly handy function to run several (probably related) Promises simultaneously,
 * allowing for any given Promise to reject, results will be returned in an object with same key names as the input
 */

/* example:
 * const x = {
 *    api1: () => callApi1(),
 *    api2: () => callApi2(),
 *    api3: () => callApi3(),
 * };
 * const r = await multiApiCall(x);
 * // r = { api1: api1results, api2: api2results, api3: api3results }
 */

/* for a more interesting exercise, say you have 3 items that you want to call 3 different remote APIs on
 * so you want to make 9 simultaneous API calls to get the data as fast as you can, and await all of them to complete.
 * you can do this by creating an array of 'x' objects like above, let's call it 'arr', then do:
 * const apiCalls = arr.map(api => multiApiCall(api));
 * const res = await Promise.all(apiCalls);
 */

function multiApiCall(obj) {
    const funcs = Object.entries(obj);
    const promises = funcs.map(([name, func]) => (
            func && func.call()
            .then(ret => (console.warn('* ', name, 'returns'), [name, ret]))
            .catch(err => {
                console.warn('**** Error in ', func, ':', err);
                return [name, err];
            }) || [name, undefined]
        )
    );
    return Promise.all(promises).then(arr => (
        arr.reduce((accumulator, [name, ret]) => (accumulator[name] = ret, accumulator), {})
    ));
}