Write a function like,
module.exports = (ctx) => {
ctx.body = 'hello world'
}then deploy it with fx up command,
$ fx up -p 8080 func.jstest it using curl
$ curl 127.0.0.1:8080
HTTP/1.1 200 OK
Connection: keep-alive
Content-Length: 11
Content-Type: text/plain; charset=utf-8
Date: Tue, 06 Aug 2019 15:58:41 GMT
hello world