How Can I Execute Async Functions Concurrently in JavaScript?

Executing Async Functions Concurrently

In ES7/ES2016, using multiple await statements does not execute the functions in parallel. Instead, they are executed sequentially, much like chaining .then() with promises.

Example:

await someCall();
await anotherCall();

In this example, anotherCall() will only be called once someCall() is completed.

Parallelizing Async Function Calls

To execute async functions in parallel, there are a few options:

Using Promise.all()

The simplest approach in Node.js is to use Promise.all() to wrap the async functions you want to execute concurrently:

await Promise.all([someCall(), anotherCall()]);

This will create a single promise that represents the completion of all the input promises.

Storing the Results

If you need to store the results, you can use destructuring in the await statement:

let [someResult, anotherResult] = await Promise.all([someCall(), anotherCall()]);

Note on Error Handling

Promise.all will fail fast. This means that if any of the input promises rejects, the entire operation will be rejected with that error.

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