• Last Updated: 13 Mar 2025
• Category
• Arvind Das
expressjs webpack build docker

Creating docker image for a vanilla expressjs app

Hi Everyone,

Today we will see in simple steps of how to create build or create docker image build with plain express js with javascript. The process is quite simple.

You will need to install babel-loader, webpack and webpack-cli as dev dependencies. Your package.json should look like this

"devDependencies": {
    "babel-loader": "^10.0.0",
    "webpack": "^5.98.0",
    "webpack-cli": "^6.0.1"
  }

This will make sure that you have the cli available to execute the webpack build command. Now lets have a look at webpack.config.js

 // webpack.config.js
 const path = require('path');


 module.exports = {
   target: 'node', 
   entry: './index.js', 
   output: {
     filename: 'bundle.js',
     path: path.resolve(__dirname, 'dist'),
   },
   module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: 'babel-loader',
      },
    ],
  },
   // Additional configuration goes here
 };

This is a very simple file but takes care of the important bundling steps by default. More can be enabled with plugins. Lets look at the dockerfile

  # Build stage
  FROM node:22-slim AS builder
  WORKDIR /build
  COPY package*.json ./
  
  
  # Install all dependencies including devDependencies
  RUN npm install
  
  
  # Install babel-related packages explicitly if needed
  RUN npm install --save-dev @babel/core @babel/preset-env babel-loader webpack webpack-cli
  
  
  COPY . .
  RUN npm run build
  
  
  
  # Production stage
  FROM node:22-slim
  ENV NODE_ENV=production
  WORKDIR /app
  
  
  # Only copy production necessary files
  COPY --from=builder /build/package*.json ./
  COPY --from=builder /build/dist ./dist     
  # COPY --from=builder /build/dist/node_modules ./node_modules
  
  
  # Starting our application
  # Adjust the path based on your build output
  CMD [ "node", "dist/bundle.js" ]  
  
  
  # Exposing server port
  EXPOSE 3000

1. The above Dockerfile steps make sure that build is properly done
2. No source code goes into the build.

By Following the steps above, you should have a working image for your app. You can also run the build step using

 "build": "webpack --config webpack.config.js"

Hope it helps. Cheers!