Node.js检测到两个猫鼬发现完成的时间

Question

我正在尝试使用此库初始化带有自动完成功能的两个输入.当我加载页面时,我将触发Ajax来初始化两个输入文本.

但我不知道当我的猫鼬发现完成时我怎么能发现.

这是我的服务器端代码:

app.post('/init/autocomplete', function(req, res){
    var autocomplete = {
        companies: [],
        offices: []
    };

    // Find all companies
    Company.find({}, function(err, companies) {
        if (err) throw err;

        companies.forEach(function(company) {
            autocomplete.companies.push({value: company.name})
        });

        console.log('One');
    });

    // Find all offices
    Office.find({}, function(err, offices) {
        if (err) throw err;

        offices.forEach(function(office) {
            autocomplete.offices.push({value: office.name})
        });

        console.log('Two');
    });

    console.log('Three');

    // res.json(autocomplete);
});

我知道find方法是异步的.这就是为什么我按以下顺序看到我的console.log():

Three
One
Two

如何完成并完成console.log('Three');时如何触发？Company.findOffice.find

我想看看console.log('Three');最后一个位置.

编辑:

我想我可以这样做:

app.post('/init/autocomplete', function(req, res){
    var autocomplete = {
        companies: [],
        offices: []
    };

    // Find all companies
    Company.find({}, function(err, companies) {
        if (err) throw err;

        companies.forEach(function(company) {
            autocomplete.companies.push({value: company.name})
        });

        // Find all offices
        Office.find({}, function(err, offices) {
            if (err) throw err;

            offices.forEach(function(office) {
                autocomplete.offices.push({value: office.name})
            });

            res.json(autocomplete);
        });
    });
});

但我不知道这是不是好方法.也许使用诺言会更好？我愿意接受所有建议.

Answer 1

Mongoose 内置了对 promises 的支持，它提供了一种干净的方式来等待多个异步查询操作的完成Promise.all：

// Tell Mongoose to use the native Node.js promise library.
mongoose.Promise = global.Promise;

app.post('/init/autocomplete', function(req, res){
    var autocomplete = {
        companies: [],
        offices: []
    };

    // Call .exec() on each query without a callback to return its promise.
    Promise.all([Company.find({}).exec(), Office.find({}).exec()])
        .then(results => {
            // results is an array of the results of each promise, in order.
            autocomplete.companies = results[0].map(c => ({value: c.name}));
            autocomplete.offices = results[1].map(o => ({value: o.name}));
            res.json(autocomplete);
        })
        .catch(err => {
            throw err; // res.sendStatus(500) might be better here.
        });
});