NodeJS: callback not a function - node.js

Question

I've checked the other questions but none form an answer to mine. In other words: no answer works.
I've got two modules: app and logic. App passes a callback to logic, which logic then calls. However I get the error "cb is not a function". That's it, no more information.
This is the function in app.js that poses the callback:
app.get('/assignments/open/:student', function (request, response) {
var callback = function(mail, jobtitle) {
response.status(200).json(logic.getOpenAssignments(request.params.student));
}
logic.examine(request, callback);
});
This is the function in logic.js that calls the callback:
examine: function (request, cb) {
var options = {
host: 'graph.microsoft.com',
path: '/v1.0/me',
method: 'GET',
headers: {
'Content-Type': 'application/json',
'Authorization': request.get('Authorization')
}
};
var req = http.get(options, function(res) {
res.on('data', function(chunk) {
chunk = JSON.parse(chunk);
mail = chunk['mail'];
jobtitle = chunk["jobTitle"];
cb(mail, jobtitle);
})
});
},
Any solutions? Thanks in advance!
Edit:
Following code doesn't work:
examine: function (request, cb) {
var options = {
host: 'graph.microsoft.com',
path: '/v1.0/me',
method: 'GET',
headers: {
'Content-Type': 'application/json',
'Authorization': request.get('Authorization')
}
};
var req = http.get(options, res => {
res.on('data', chunk => {
chunk = JSON.parse(chunk);
mail = chunk['mail'];
jobtitle = chunk["jobTitle"];
cb(mail, jobtitle);
})
});
},
Following code also doesn't work, does this mean the scope is not the problem?
examine: function (request, cb) {
var options = {
host: 'graph.microsoft.com',
path: '/v1.0/me',
method: 'GET',
headers: {
'Content-Type': 'application/json',
'Authorization': request.get('Authorization')
}
};
cb('hehe', 'hoho');
},

Answer 1

If you're using ES6, try to use arrow function to pass the scope to http.get's callback function:
var req = http.get(options, res => {
res.on('data', chunk => {
chunk = JSON.parse(chunk);
mail = chunk['mail'];
jobtitle = chunk["jobTitle"];
cb(mail, jobtitle);
})
});
Or you could also pass cb to your callback function :
var req = http.get(options, function(res, cb) {
res.on('data', function(chunk, cb) {
chunk = JSON.parse(chunk);
mail = chunk['mail'];
jobtitle = chunk["jobTitle"];
cb(mail, jobtitle);
})
});

Answer 2

Maybe the issue is, you are not waiting for data chunk to process. Try the following snippet. Added a way to convert http.get to promises(very common) and this avoids passing all the messy callbacks.
//put this somewhere inside where examine is located.
logic.httpGet = options => {
return new Promise((resolve, reject) => {
http.get(options, res => {
res.setEncoding('utf8');
let body = '';
res.on('data', chunk => body += chunk);
res.on('end', () => resolve(body));
}).on('error', reject);
});
};
//convert your route like this
app.get('/assignments/open/:student', function (request, response) {
cont options = {
host: 'graph.microsoft.com',
path: '/v1.0/me',
method: 'GET',
headers: {
'Content-Type': 'application/json',
'Authorization': request.get('Authorization')
}
};
return logic
.httpGet(options)
.then((data)=>{
const data =JSON.parse(data);
//i don't see where you use the processed data but do whatever you want below here
repsonse.status(200).json(logic.getOpenAssignments(request.params.student))
})
})