Prerequisite: To follow along with this article, you need to know the basics of promises.

In Node.js, the typical way to achieve concurrency is by using one of the promise methods — the most common being Promise.all().

Imagine you want to query a database with a list of IDs for a list of users and you want to act on the data returned (e.g. create a new user if the ID didn’t return a user).

One way to do this would be:

async function findOrCreateUser(id){
const user = await findUser(id)
if(!user){
return await createUser(id)
}
return user
}

async function run(idList){
  let userList = []
  for await (const id of idList){
 const user = await findOrCreateUser(id)
 userList.push(user)
  }
}

#javascript #software-development #promises #programming #nodejs