I've got two separate apps (frontend and backend) running on heroku. Let's say frontend can be accessed through http://frontend-app.url and backend through http://backend-app.url The front end app runs on node.js using express. I want my frontend app to call backend app api, but I can't make it call anything other than the same domain that frontend is deployed.
In server.js i got the following lines, which supposedly should reroute the api calls.
app.get('/data', (req, res) => {
    res.json({url: 'http://backend-app.url'})
});
All api urls start with /data. I start my app by node server.js.
First call when accessing the frontend app is always /data/units, but it always calls http://frontend-app.url/data/units instead of http://backend-app.url/data/units.
How do I make this right?
 
    