Weekly Awesome JS KT Part-2: Promise.all() vs multiple awaits

Imagine you have a case where you want to retrieve some information about a list of users, and for each user you have to hit the endpoint and await a promise, how will you do it? I came across a similar problem(I am giving a simplified version of the problem I came across not the full code), and the approach I took was something like this:

First I created a async function which handles all the logic of updating and getting a particular user from its id

const updateUser = async ({userId}:{userId:string})=>{ await updateUserDetails(userId) } userIds = [....] // loop for each userId and update it for(const id of userIds) { await updateUser({userId: id}) } 

But there is a problem with this code, let me explain with a more simplified example:

const test1 = async () => { const delay1 = await Promise.delay(600); const delay2 = await Promise.delay(600); const delay3 = await Promise.delay(600); }; const test2 = async () => { await Promise.all([ Promise.delay(600), Promise.delay(600), Promise.delay(600)]); }; 

Here test1 takes almost ~1800ms to run since it runs sync each promises whereas test2 takes ~600ms to runs since it runs all promises in parallel

So a faster version of the code snippet one would be something like this:

const updateUser = async ({userId}:{userId:string})=>{ await updateUserDetails(userId) } userIds = [....] await Promise.all(userIds.map((userId)=>updateUser({userId}))) 

Keep Exploring 🛥️

https://stackoverflow.com/questions/45285129/any-difference-between-await-promise-all-and-multiple-await