Get random wiki page from cloud functions - json

Question

I tried to get a random Wikipedia page over their API via Google Cloud Functions. The Wikipedia API works fine. This is my request:
https://de.wikipedia.org/w/api.php?action=query&format=json&generator=random
For testing you can change the format to jsonfm in see the result in the browser. Click here 👍.
But it seems that my functions get destroyed even before the request was completely successfully. If I want to parse the data (or even if I want to log that data) I got a
SyntaxError: Unexpected end of json
The log look like (for example) that (no I haven't cut it by myself):
DATA: ue||"},"query":{"pages":{"2855038":{"pageid":2855038,"ns":0,"title":"Thomas Fischer
Of course, that is not a valid json and can't be parsed. Whatever this is my function:
exports.randomWikiPage = function getRandomWikiPage (req, res) {
const httpsOptions = {
host: "de.wikipedia.org",
path: "/w/api.php?action=query&format=json&generator=random"
};
const https = require('https');
https.request(httpsOptions, function(httpsRes) {
console.log('STATUS: ' + httpsRes.statusCode)
console.log('HEADERS: ' + JSON.stringify(httpsRes.headers))
httpsRes.setEncoding('utf8')
httpsRes.on('data', function (data) {
console.log("DATA: " + data)
const wikiResponse = JSON.parse(data);
const title = wikiResponse.query.title
res.status(200).json({"title": title})
});
}).end();
};
I've already tried to return something here. Like that video explained. But as I look into the node docs https.request don't return a Promise. So return that is wrong. I've also tried to extract the on('data', callback) into it's own function so that I can return the callback. But I haven't a success with that either.
How have to look my function that it return my expected:
{"title": "A random Wikipedia Page title"}
?

Answer 1

I believe your json comes through as a stream in chunks. You're attempting to parse the first data chunk that comes back. Try something like:
https.request(httpsOptions, function(httpsRes) {
console.log('STATUS: ' + httpsRes.statusCode)
console.log('HEADERS: ' + JSON.stringify(httpsRes.headers))
httpsRes.setEncoding('utf8')
let wikiResponseData = '';
httpsRes.on('data', function (data) {
wikiResponseData += data;
});
httpRes.on('end', function() {
const wikiResponse = JSON.parse(wikiResponseData)
const title = wikiResponse.query.title
res.status(200).json({"title": title})
})
}).end();
};