“返回等待"是否存在性能问题? [英] Are there performance concerns with `return await`?

问题描述

我看到有一个 eslint 规则，no-return-await，用于禁止return await.

I see there is an eslint rule, no-return-await, for disallowing return await.

在规则的描述中，它声明 return await 添加 在总体 Promise 解决或拒绝之前的额外时间".

In the rule's description, it states a return await adds "extra time before the overarching Promise resolves or rejects".

但是，当我查看 MDN async 函数文档，简单示例"显示了一个包含 return await 的示例，但没有说明这可能是性能问题的原因.

However, when I look at MDN async function docs, the "Simple Example" shows an example containing return await without any description of why this might be a performance problem.

return await 是 eslint 文档建议的实际性能问题吗?

Is return await an actual performance problem as the eslint docs suggest?

如果是，怎么办?

推荐答案

不，没有任何性能问题.这只是一个不必要的额外操作.执行可能需要更长的时间，但应该几乎不会引起注意.对于整数x，它类似于return x+0 而不是return x.或者更确切地说，完全等同于毫无意义的.then(x => x).

No, there isn't any performance problem. It's just an unnecessary extra operation. It might take a bit longer to execute, but should be hardly noticeable. It's akin to return x+0 instead of return x for an integer x. Or rather, exactly equivalent to the pointless .then(x => x).

它不会造成实际伤害，但我认为它的风格很糟糕，表明作者没有完全理解­hend promises 和 async/await.

It doesn't do actual harm, but I'd consider it bad style and a sign that the author does not fully compre­hend promises and async/await.

但是，有一种情况会产生重要影响:

However, there's one case where it make an important difference:

try {
    …
    return await …;
} …

await 确实抛出拒绝，并且在任何情况下都等待在 catch 或 finally 处理程序执行之前的承诺解析.一个简单的 return 会忽略它.

await does throw on rejections, and in any case awaits the promise resolution before catch or finally handlers are executed. A plain return would have ignored that.

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