Good time to use Promise.all()

Published 2021-09-30

Today I will talk about the good time to use Promise.all().

Why? (The Motivation Behind)

As you might have known, we could use Promise.all() to run multiple async operations concurrently. Let me elaborate some characteristics about Promise.all:

  • We will only get response(callback) when all the async operations finished (whether success or failed).
  • We could group several async operation and have them run concurrently and only proceed when all of them completed.

The above points leads to:

  • Better Performance since we could execute all of them concurrently
  • Better Grouping of Logic. When we could group several async operations related with each otherm, it will look cleaner and easier to understand from the code as well.

Next, we will real code example on how some good time to use Promise.all


Below scenario is a series of validation to check when sending withdrawal request to backed and we need to query database to get this information.

👎 example. This example was not optimized because we get the balance 1st, then only proceed to retrieve the conversion rate.

// Check has balance const balance = await transactionService.getBalance() // Get conversion rates const conversionRate = await conversionRatesService.getConversionRates()

👍 example. Good example is we could optimized them and call them concurrently.

// Check has balance const [balance, conversionRate] = await Promise.all([ transactionService.getBalance(), conversionRatesService.getConversionRates(), ])