Docker angular instance can't get data from Docker express instance - angularjs

Question

Through Docker compose I build up a set of images. Among them, there's a node.js/express server and an angularjs 2.0 frontend.
Here's the docker-compose file:
version: "3.3"
services:
angular:
image: micheleminno/angular-client:latest
build: ./angular-client
ports:
- "4200:4200"
express:
image: micheleminno/express-server:latest
build: ./express-server
depends_on:
- mysql
- elasticsearch
ports:
- "3000:3000"
networks:
- sql
- nosql
elasticsearch:
build: elasticsearch/
ports:
- "9200:9200"
- "9300:9300"
networks:
- nosql
environment:
- MAX_OPEN_FILES=1048576
cap_add:
- IPC_LOCK
ulimits:
memlock:
soft: -1
hard: -1
command: echo "Elasticsearch disabled"
kibana:
build: kibana/
volumes:
- ./kibana/config/:/usr/share/kibana/config
ports:
- "5601:5601"
networks:
- nosql
depends_on:
- elasticsearch
command: echo "Kibana disabled"
mysql:
image: mysql:5.5
environment:
- MYSQL_ROOT_PASSWORD=password
- MYSQL_DATABASE=real-affinities
- MYSQL_USER=production
- MYSQL_PASSWORD=production
ports:
- "3306:3306"
networks:
- sql
migrations:
image: micheleminno/db-migrations:latest
environment:
- NODE_ENV=production
depends_on:
- mysql
networks:
- sql
networks:
nosql:
driver: bridge
sql:
driver: bridge
When everything starts, loading page http://localhost:4200/ triggers the following GET request to the express server:
https://localhost:3000/target
but the request doesn't succeed:
Whereas if I do by myself the GET request, I can get results correctly:
Update
Here's my CORS section in server.js:
const cors = require('cors');
const app = express();
app.use(cors());

Answer 1

You have to enable CORS in your Express Server. The CORS spec requires the OPTIONS call to precede the POST or GET if the POST or GET has any non-simple content or headers in it.
As you can see in your error pic, the target is a xhr OPTIONS request. See also the "Preflighted requests" section in the link above.
One possible and simple solution is to use the node.js package cors.

Answer 2

I changed https://localhost:3000 to http://localhost:3000 as url for the http requests from angular client and now it works.