how to test docker image locally express node.js server code example

Example 1: simple nodejs dockerfile

FROM node:12-alpine
WORKDIR /app
COPY package.json yarn.lock ./
RUN yarn install --production
COPY . .
CMD ["node", "/app/src/index.js"]

Example 2: dockerfile for nodejs

# Choose the Image which has Node installed already
FROM node:alpine

# COPY all the files from Current Directory into the Container
COPY ./ ./

# Install the Project Dependencies like Express Framework
RUN npm install

# Tell that this image is going to Open a Port 
EXPOSE 8080

# Default Command to launch the Application
CMD ["npm", "start"]