await 关键词

在顶层启用对 await 关键字的支持。

> await Promise.resolve(123)
123
> await Promise.reject(new Error('REPL await'))
Uncaught Error: REPL await
    at REPL2:1:54
> const timeout = util.promisify(setTimeout);
undefined
> const old = Date.now(); await timeout(1000); console.log(Date.now() - old);
1002
undefined

在 REPL 中使用 await 关键字的一个已知限制是它会使 const 和 let 关键字的词法范围无效。

例如：

> const m = await Promise.resolve(123)
undefined
> m
123
> const m = await Promise.resolve(234)
undefined
> m
234

--no-experimental-repl-await 应禁用 REPL 中的顶级等待。

Support for the await keyword is enabled at the top level.

> await Promise.resolve(123)
123
> await Promise.reject(new Error('REPL await'))
Uncaught Error: REPL await
    at REPL2:1:54
> const timeout = util.promisify(setTimeout);
undefined
> const old = Date.now(); await timeout(1000); console.log(Date.now() - old);
1002
undefined

One known limitation of using the await keyword in the REPL is that it will invalidate the lexical scoping of the const and let keywords.

For example:

> const m = await Promise.resolve(123)
undefined
> m
123
> const m = await Promise.resolve(234)
undefined
> m
234

--no-experimental-repl-await shall disable top-level await in REPL.