setHeader before sending: https://nodejs.org/api/http.html#http_response_setheader_name_value
res.setHeader('content-type', 'text/plain');
res.send(JSON.stringify({...}));
setHeader before sending: https://nodejs.org/api/http.html#http_response_setheader_name_value
res.setHeader('content-type', 'text/plain');
res.send(JSON.stringify({...}));