Await 的运算符优先级是什么? [英] What is the Operator Precedence of Await?

问题描述

在 Javascript 中，某些运算符先于其他运算符处理:

In Javascript certain operators are processed before others:

1 + 2 * 3
// 1 + (2 * 3)
// 7 because * has higher precedence than +

1 === 0 + 1
// 1 === (0 + 1)
// true because + has a higher precedence than ===

MDN 有一个所有运营商的完整分类 和它们的优先级……除了 await.

The MDN has a full breakdown of all operators and their precedence ... except await.

await getFoo() * 2; // await (getFoo() * 2) or (await getFoo()) * 2?
await getFoo() === 5; // await (getFoo() === 5) or (await getFoo()) === 5?

谁能解释一下在 await 之前/之后处理了哪些运算符?

Can anyone explain which operators are processed before/after await?

现在我觉得我必须添加一堆可能是不必要的括号，因为我不确定在 await 之前/之后会处理什么.虽然我知道我应该能够查到这个，但即使是 MDN(恕我直言，文档的黄金标准)也没有答案.

Right now I feel like I have to add a bunch of parenthesis that are probably unnecessary because I'm not sure what will get handled before/after await. And while I know I should just be able to look this up, even MDN (the gold standard of documentation IMHO) doesn't have the answer.

推荐答案

An AwaitExpression 是一个 UnaryExpression 和 delete、void、typeof、+ 具有相同的优先级，-、~ 和 !，绑定比任何二元运算符都强.

An AwaitExpression is a UnaryExpression and has the same precedence as delete, void, typeof, +, -, ~, and !, binding stronger than any binary operator.

这与 yield 不同，后者的优先级低于除逗号运算符之外的任何其他内容.做出这个设计决策是因为两者都yield a+b 和 await a + await b 是被认为比 (yield a) + (yield b) 和 await (a + b) 更常见的场景代码>.

This is unlike yield which has a precedence lower than anything else except the comma operator. This design decision was made because both yield a+b and await a + await b are scenarios thought to be more common than (yield a) + (yield b) and await (a + b).

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