How to allow CORS in Express JS? Explain with an example?

Express.js - Interview Questions

In order to permit CORS in Express.js, add the subsequent code in server.js :

Example :

app.all('*', function(req, res, next) {
res.set('Access-Control-Allow-Origin', '*');
res.set('Access-Control-Allow-Methods', 'GET, POST, DELETE, PUT');
res.set('Access-Control-Allow-Headers', 'X-Requested-With, Content-Type');
if ('OPTIONS' == req.method) return res.send(200);
next();
});