如何返回只有当我的回调完成

Question

我正在写一个Node.js应用程序，我无法返回我的网页刮到我的主要app.get函数的值。该页面被抓取得很好，并且它的结果使我一直回到我的回调中的RETURN，但它实际上并没有返回值。任何帮助，将不胜感激！

编辑：这必须是一个纯JavaScript的解决方案，不使用jQuery的。

在我server.js文件，我有这样的代码：

var machineDetails = helpers.scrapePage(); 

app.get('/', function (req, res) { 

    res.render('index', { machineDetails: machineDetails, title: 'VIP IT Dashboard'}); 
}); 

在helpers.js文件我有以下功能

//Requires 
httpntlm = require('httpntlm'), 
cheerio = require('cheerio'); 


var userData; 

function callSite(callback) { 

    //Scrape site and get information 
    var scrape; 

    httpntlm.get({ 
     url: "http://URLthatIamScraping.com", 
     username: 'username1', 
     password: 'password1', 
     domain: 'companyDomain' 
    }, function (err, res) { 
     if (err) return err; 

     //Sort information for the computer 
     var $ = cheerio.load(res.body); 

     var scrape = $('#assetcontent').html(); 

     //Return the html content of the page 
     callback(scrape); 

    }); 
} 


exports.scrapePage = function(){ 

    return callSite(function(data) { 

     //This is called after HTTP request finishes 
     userData = data; 

     //ISSUE: userData is not actually making it back to my server.js variable called "machineDetails" 
     return userData; 

    }); 
} 

Answer 1

它是异步的，你不能只返回值。它必须在回调中返回。

//Requires 
httpntlm = require('httpntlm'), 
cheerio = require('cheerio'); 


function callSite(callback) { 

    httpntlm.get({ 
     url: "http://URLthatIamScraping.com", 
     username: 'username1', 
     password: 'password1', 
     domain: 'companyDomain' 
    }, function (err, res) { 
     if (err) return callback(err); 

     //Sort information for the computer 
     var $ = cheerio.load(res.body); 

     var scrape = $('#assetcontent').html(); 

     //Return the html content of the page 
     callback(null, scrape); 

    }); 
} 


exports.scrapePage = callSite; 

然后你做：

app.get('/', function (req, res, next) { 
    helpers.scrapePage(function(error, machineDetails) { 
     if(error) return next(error); 
     res.render('index', { machineDetails: machineDetails, title: 'VIP IT Dashboard'}); 
    }); 
});