Node.js的：如何运行code顺序异步 [英] Node.js: How to run asynchronous code sequentially

问题描述

我有code的这个块

User.find({}, function(err, users) {
    for (var i = 0; i < users.length; i++) {
        pseudocode
        Friend.find({
            'user': curUser._id
        }, function(err, friends) * * ANOTHER CALLBACK * * {
            for (var i = 0; i < friends.length; i++) {
                pseudocode
            }
            console.log("HERE I'm CHECKING " + curUser);
            if (curUser.websiteaccount != "None") {
                request.post({
                    url: 'blah',
                    formData: blah
                }, function(err, httpResponse, body) { * * ANOTHER CALLBACK * *
                        pseudocode
                    sendMail(friendResults, curUser);
                });
            } else {
                pseudocode
                sendMail(friendResults, curUser);
            }
        });
        console.log("finished friend");
        console.log(friendResults);
        sleep.sleep(15);
        console.log("finished waiting");
        console.log(friendResults);
    }
});

有一对夫妇异步事情发生在这里。对于每一个用户，我想找到自己的朋友有关，并将其Concat的一个变量。然后，我要检查，如果该用户有一个网站账号，如果是这样，做一个POST请求并有抓住一些信息。唯一的一点是，这一切正在发生无序自code未等待回调结束。我一直在使用睡眠，但这并不解决任何因为它仍然混乱的问题。

There's a couple asynchronous things happening here. For each user, I want to find their relevant friends and concat them to a variable. I then want to check if that user has a website account, and if so, make a post request and grab some information there. Only thing is, that everything is happening out of order since the code isn't waiting for the callbacks to finish. I've been using a sleep but that doesn't solve the problem either since it's still jumbled.

我看着成异步，但这些功能相互交织，并没有真正分开，所以我不知道它会如何与工作异步两种。

I've looked into async, but these functions are intertwined and not really separate, so I wasn't sure how it'd work with async either.

任何建议得到这code按顺序运行？

Any suggestions to get this code to run sequentially?

谢谢！

推荐答案

我preFER承诺模块为q的 https://www.npmjs.com/package/promise 因为它的简单

I prefer the promise module to q https://www.npmjs.com/package/promise because of its simplicity

var Promises = require('promise');
var promise = new Promises(function (resolve, reject) {
    // do some async stuff
    if (success) {
        resolve(data);
    } else {
        reject(reason);
    }
});
promise.then(function (data) {
    // function called when first promise returned
    return new Promises(function (resolve, reject) {
        // second async stuff
        if (success) {
            resolve(data);
        } else {
            reject(reason);
        }
    });
}, function (reason) {
    // error handler
}).then(function (data) {
    // second success handler
}, function (reason) {
    // second error handler
}).then(function (data) {
    // third success handler
}, function (reason) {
    // third error handler
});

正如你所看到的，你可以继续这样下去。您也可以从异步处理程序返回简单的值，而不是承诺，然后这些将简单地传递给然后回调。

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