How to catch an empty reply from an API {} - node.js

Question

I'm currently using Node.js to fetch an API data and converting it into my own Express.js API server to send my own data (The 2 APIs I'm using changes the structure sometime and I have some users that need to keep the same structure).
So here is the code I'm using
app.get('/app/account/:accountid', function (req, res) {
return fetch('https://server1.com/api/account/' + req.params.accountid)
.then(function (res) {
var contentType = res.headers.get("content-type");
if (contentType && contentType.includes("application/json")) {
apiServer = 'server1';
return res.json();
} else {
apiServer = 'server2';
throw "server1 did not reply properly";
}
}).then(server1Reconstruct).then(function (json) {
res.setHeader('Content-Type', 'application/json');
return res.send(json);
}).catch(function (err) {
console.log(err);
}).then(function () {
if (apiServer == 'server2') {
server2.fetchAccount({
accountID: [Number(req.params.accountid)],
language: "eng_us"
})
.then(server2Reconstruct)
.then(function (json) {
res.setHeader('Content-Type', 'application/json');
return res.send(json);
}).catch(function (err) {
console.log(err);
});
}
});
})
To quickly explain the code: I call server1 through a normal Fetch this answer might be {} which is where I have a problem. If the accountid doesn't exist the server returns an JSON response with no errors to grab...
What should I do to be able to catch it... And If I catch it switch to server 2.
(Don't be too confused about server2 call as it's another package).

Answer 1

If I understand your problem correctly, you should follow those steps :
fetch the initial API
call the .json() method on the result - which returns a promise
deal with the json response in the first .then(json => ...), and here check if the result is {} then call server2, else call server1
BTW, your code looks very messy with all those then and catch, I recommend putting some stuff into functions, and using async/await if you can.
Here is some pseudo-code sample that you could use :
function server2Call() {
return server2.fetchAccount({
accountID: [Number(req.params.accountid)],
language: 'eng_us'
})
.then(server2Reconstruct)
.then(function (json) {
res.setHeader('Content-Type', 'application/json');
return res.send(json);
}).catch(function (err) {
console.log(err);
});
}
app.get('/app/account/:accountid', function (req, res) {
return fetch('https://server1.com/api/account/' + req.params.accountid)
.then(res => {
var contentType = res.headers.get('content-type');
if (contentType && contentType.includes('application/json')) {
return res.json();
} else {
server2Call()
}
})
.then(json => {
res.setHeader('Content-Type', 'application/json');
if (json is {}) return server2Call()
else return res.send(json);
}).catch(function (err) {
console.log(err);
})
});