Basic Commands for DockerFile:

                      FROM node:10
                      WORKDIR /app
                      COPY package.json /app
                      RUN npm install
                      COPY . /app
                      EXPOSE 3000
                      CMD npm start

 Command to convert the node app to a docker image:

 > docker build ./
 this will run the DockerFile and path  of ./ or any PATH should point towards the DockerFile this will output the Image file.

 We can give tags also which will be easy to identify the Docker Files
 > docker build ./ -t myapp

 this will give output:
Successfully built b1bff2dcdbc7
Successfully tagged myapp:latest

check in docker images