no-return-await.md

Disallows unnecessary return await (no-return-await)

Using return await inside an async functionkeeps the current function in the call stack until the Promise that is being awaited have resolved. You can take a shortcut and just return the Promise right away to avoid this, saving an extra microtask before resolving the overarching Promise.

The only visible change when doing this is that the function will no longer be a part of the stack trace, if an error is thrown asyncrously from the Promise being returned.

Rule Details

This rule aims to prevent a likely common performance hazard due to a lack of understanding of the semantics of async function.

Examples of incorrect code for this rule:

async function foo() {
    return await bar();
}

Examples of correct code for this rule:

async function foo() {
    return bar();
}

async function foo() {
    await bar();
    return;
}

async function foo() {
    const x = await bar();
    return x;
}

async function foo() {
    try {
        return await bar();
    } catch (error) {}
}

In the last example the await is necessary to be able to catch errors thrown from bar().

When Not To Use It

There are a few reasons you might want to turn this rule off:

• If you want to use await to denote a value that is a thenable
• If you do not want the performance benefit of avoiding return await
• If you still want the functions to show up in stack traces

Further Reading

async function on MDN

await vs return vs return await by Jake Archibald