nginx angular 5 reverse-proxy mongo image

I been able to get the reverse proxy working for my angular 5 project. With below files. I am very new to Angular and nginx. Before I dockerized the client and nginx etc. I just installed everything under one path. So I just ran one npm install and I worked with npm start, ng build --prod and ng serve.

I am just a bit confused about Angular 2 version 5, I thought I was trying to separate the client from the server. Knowing that Angular 2 runs most things client side. However right now it looks like my app.js is still being called from within the same 'client' container. Am I supposed to separate and containerize the express server and what are the benefits of doing this?

I am also going to run mongo image from a container. Am I correct in linking the Client container to mongo?

nginx default.conf

   server {
location / {
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_pass http://client:4200/;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
   }
}

docker-compose.yml

   version: '2'

services:
  # Build the container using the client Dockerfile
   client:
   build: ./
  # This line maps the contents of the client folder into the container.
   volumes:
    - ./:/usr/src/app
    links:
     - mongo
    depends_on:
    - mongo
  mongo:      
    image: mongo
    container_name: "mongodb"
    environment:           
    - MONGO_DATA_DIR=/data/db
    - MONGO_LOG_DIR=/dev/null
   volumes:
    - ./data/db:/data/db
   ports:
    - 27017:27017
   command: mongod --smallfiles --logpath=/dev/null # --quiet
  # Build the container using the nginx Dockerfile
 nginx:
  build: ./nginx
   # Map Nginx port 80 to the local machine's port 80
  ports:
    - "80:80"
   # Link the client container so that Nginx will have access to it
  links:
    - client

Dockerfile

  #  Create a new image from the base nodejs 7 image.
 FROM node:8.1.4-alpine as builder
 # Create the target directory in the imahge
 RUN mkdir -p /usr/src/app
 # Set the created directory as the working directory
 WORKDIR /usr/src/app
# Copy the package.json inside the working directory
 COPY package.json /usr/src/app
 # Install required dependencies
 RUN npm install 
 # Copy the client application source files. You can use .dockerignore
 to     exlcude files. Works just as .gitignore does.
 COPY . /usr/src/app
 # Open port 4200. This is the port that our development server uses
 EXPOSE 3000
 # Start the application. This is the same as running ng serve.
 CMD ["npm", "start"]