从nodejs向客户端发送数据不起作用

Question

I am trying to send a status message to client via ajax call using GET method. My data to Nodejs server goes through fine, but i cannot send back the data to my client.I am using expressjs as my framework. I know the data exists because when I console.log(error) I get a object such as {[Error:test@test.com is already subsribed]} but i cannot output this message to client.

Here is the route.js: it captures (\\subscribe) on app.js

function signUp(name, email){
    var MailChimpAPI = require('mailchimp').MailChimpAPI;
    var API_KEY = 'asdfasdf',
            LIST_ID = 'asdfasdfas';
  var api = new MailChimpAPI(API_KEY , { version : '1.3', secure : false });
    var names = name.split(' '), status;
    var data ={
            apikey: API_KEY,
            id: LIST_ID,
            email_address : email,
            merge_vars: {'FNAME': names[0], 'LNAME': names[1]},
            double_optin: false,
            send_welcome: true
        };

     api.listSubscribe(data, function(error) {

            if(error != null){
                console.log(error);
                status = error;
            }else {
            console.log('success');
                status= '{success}';
            }
        });

    return status;
}


exports.send = function(req, res, next){
    var name = req.query.name, email = req.query.email;
    res.writeHead(200, {"Content-Type": "json"});
    res.send(signUp(name, email));
    res.end();

}

Here is my client side: (returns null)

$.ajax({
    url:'subscribe',
    method: 'GET',
    data: {name: name, email: email},
    dataType: 'JSON',
    success: function(res){
    alert(res);
    }

Answer 1

I don't know the API (mailchimp) you're using, so the solution might be totally wrong. But generally you can see the difference between synchronous and asynchronous programming. Please read some tutorials to fully understand the Node.js way, because it takes some time to embrace this kind of programming :-)

The most important thing is that functions typically don't return values, but call a callback-function (sometimes not named callback but done ) when they are ready or an error was encountered.

function signUp(name, email, callback) { // <----- provide a callback
    var MailChimpAPI = require('mailchimp').MailChimpAPI;
    var API_KEY = 'asdfasdf',
        LIST_ID = 'asdfasdfas';
    var api = new MailChimpAPI(API_KEY, { version: '1.3', secure: false });
    var names = name.split(' '), status;
    var data = {
        apikey: API_KEY,
        id: LIST_ID,
        email_address: email,
        merge_vars: {'FNAME': names[0], 'LNAME': names[1]},
        double_optin: false,
        send_welcome: true
    };

    api.listSubscribe(data, function (error, result) {
        if (error) {
            console.log(error);
            callback(error); // <--- this is one of the "exit"-points of the function
        } else {
            console.log('success');
            callback(null, result); // <--- this is another
        }
    });
    // <----------- no return! nobody cares about the return value.
}


exports.send = function (req, res, next) {
    var name = req.query.name, email = req.query.email;
    res.writeHead(200, {"Content-Type": "json"});
    signUp(name, email, function (err, result) {

        // this function gets called when signUp is done (maybe seconds later)

        if (err) {
            res.send(500);
            return;
        }
        // don't know what the result looks like
        res.send({status: 'success'});
        // res.end(); DON'T USE res.end() in express!
    });
};