Disallows unnecessary return await
(no-return-await)
Inside an async function
, return await
is useless. Since the return value of an async function
is always wrapped in Promise.resolve
, return await
doesn't actually do anything except add extra time before the overarching Promise resolves or rejects. This pattern is almost certainly due to programmer ignorance of the return semantics of async function
s.
Rule Details
This rule aims to prevent a likely common performance hazard due to a lack of understanding of the semantics of async function
.
The following patterns are considered warnings:
async function foo() {
return await bar();
}
The following patterns are not warnings:
async function foo() {
return bar();
}
async function foo() {
await bar();
return;
}
async function foo() {
const x = await bar();
return x;
}
When Not To Use It
If you want to use await
to denote a value that is a thenable, even when it is not necessary; or if you do not want the performance benefit of avoiding return await
, you can turn off this rule.
Further Reading
Version
This rule was introduced in ESLint 3.10.0.