Question

鉴于我在命令行中使用node fileName.js 运行的以下代码，它似乎在循环中运行 all 项目，然后在最后睡眠......有点像是全部并行运行。

我希望代码在setTimeout期间阻止/暂停，而不是仅在setTimeout完成后运行该函数。或者，如果setTimeout不正确，则使用不同的方法，在此用例中。

const removeUsers = async () => { const users = await db.getUsers(); // returns 32 users. // Split the users up into an array, with 2 users in each 'slot'. var arrays = [], size = 2; while (users.length > 0) { arrays.push(users.splice(0, size)); } // Now, for each slot, delete the 2 users then pause for 1 sec. arrays.forEach(a => { console.log(++counter;); // Delete 2x users. a.forEach(async u => { console.log('Deleting User: ' + u.id); await 3rdPartyApi.deleteUser({id: u.id}); }); // Now pause for a second. // Why? 3rd party api has a 2 hits/sec rate throttling. setTimeout(function () { console.log('Sleeping for 1 sec'); }, 1000); }); }

并且日志是这样的..

1. Deleting User: 1 Deleting User: 2 2. Deleting User: 3 Deleting User: 4 3. ... (sleep for 1 sec) (sleep for 1 sec) (sleep for 1 sec) ... end.

看看睡眠是不是感觉它会阻塞..它只是触发一个睡眠命令，然后在一秒钟后处理......

这就是我真正追求的......

1. Deleting User: 1 Deleting User: 2 (sleep for 1 sec) 2. Deleting User: 3 Deleting User: 4 (sleep for 1 sec). 3. ... end.

Answer 1

这会调用一堆async函数。它们各自返回一个promise（async函数总是返回promises），并且这些promise将被丢弃，因为Array#forEach对它传递的函数的返回值没有任何作用。

a.forEach(async u => {
    console.log('Deleting User: ' + u.id);
    await 3rdPartyApi.deleteUser({id: u.id});
});

这启动了一个计时器，甚至没有尝试等待它。

setTimeout(function () { console.log('Sleeping for 1 sec'); }, 1000);

将计时器拆分为一个函数，该函数返回在适当的时间内解析的promise（如果您使用的是Bluebird，则可以Promise.delay使用）：

const delay = ms =>
    new Promise(resolve => {
        setTimeout(resolve, ms);
    });

并将所有内容保存在一个async函数中，这样您就不会丢弃任何承诺：

function* chunk(array, size) {
    for (let i = 0; i < array.length;) {
        yield array.slice(i, i += size);
    }
}

const removeUsers = async () => {
    const users = await db.getUsers(); // returns 32 users.

    for (const a of chunk(users, 2)) {
        console.log(++counter);

        // Delete 2x users.
        for (const u of a) {
            console.log('Deleting User: ' + u.id);
            await ThirdPartyApi.deleteUser({id: u.id});
        }

        console.log('Sleeping for 1 sec');
        await delay(1000);
    }
};

尝试使用setTimeout

1 个答案: