javascript - 如何在 Node js中的foreach之后发送响应？

Question

在我的 foreach 中，我想将数据推送到数组中并将响应发送到客户端。

我正在使用以下内容:

try {
    var allData = [];
    var venuesData = req.db.collection('venues').find({ "restaurantcompetitors": {$exists: true, $ne: null } }, {restaurantcompetitors:1});

    venuesData.forEach(function(data) {
        Array.prototype.push.apply(allData, data);

        res.status(200).send({data: allData, code: 0});
    });

}
catch (error) {
    console.log('Error found in catch: ',error);
}

但是我收到一个错误“header already sent”，因为我在循环内发送。但是如果我尝试在循环后推送数据，它就无法推送...

Answer 1

您实际上需要使用 promise 或使用 async/await

在此处阅读有关异步代码和 promise 的更多信息 - https://medium.com/dev-bits/writing-neat-asynchronous-node-js-code-with-promises-32ed3a4fd098

更多关于 async/await 的信息 - https://blog.risingstack.com/mastering-async-await-in-nodejs/

try {
    var allData = [];
    var venuesData = await req.db.collection('venues').find({
        "restaurantcompetitors": {
            $exists: true,
            $ne: null
        }
    }, {
        restaurantcompetitors: 1
    });

    // This code won't run until the venuesData has resolved
    venuesData.forEach(function (data) {
        Array.prototype.push.apply(allData, data);


    });
    //Need to send after you have done the loop
    res.status(200).send({
        data: allData,
        code: 0
    });

} catch (error) {
    console.log('Error found in catch: ', error);
}