Await vs. Promise Return: Which Should You Use in Error Handling?

Waiting vs. Returning Promises: Understanding await vs. promise Returns

Introduction:

In JavaScript, handling asynchronous tasks can be achieved using promises. When dealing with promises in async functions, a common dilemma arises: should you use return await promise or simply return promise? This article explores the differences between these two approaches, highlighting their behavioral nuances and error-handling implications.

Behavior and Performance:

In general, there is no significant difference in observable behavior between using return await promise and return promise. Both approaches yield the same promise result and have negligible performance variations. However, the implementation may slightly favor the return await version due to the potential creation of an intermediate Promise object.

Error Handling:

The key difference emerges when return or return await is used within a try-catch block. Let's consider the code snippet:

async function rejectionWithReturnAwait () {
  try {
    return await Promise.reject(new Error())
  } catch (e) {
    return 'Saved!'
  }
}

async function rejectionWithReturn () {
  try {
    return Promise.reject(new Error())
  } catch (e) {
    return 'Saved!'
  }
}

In rejectionWithReturnAwait, the async function awaits the rejected promise before returning its result. This triggers an exception, which is caught by the catch clause, leading the function to return a promise that resolves to "Saved!".

In contrast, rejectionWithReturn returns the rejected promise directly without awaiting it within the async function. Consequently, the catch case is not invoked, and the promise rejection is propagated to the caller.

Conclusion:

In most cases, both return await promise and return promise yield the same behavior. However, when error handling is involved within try-catch blocks, return await promise ensures the promise is awaited and exceptions are caught by the enclosing function, while return promise directly returns the promise without error handling within the function.

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