Bundling Your Node.js Express App with esbuild

When setting up a backend node project, I have almost always defaulted to setting up a TypeScript to build the app using the outDir property in tsconfig.json.

// tsconfig.json
{
  "compilerOptions": {
    ...
    "outDir": "./built",
    ...
  }
}

This worked well for local development as the node_modules folder sits right there and running the built file is a simple node built/index.js.

This did not work so well when it came time to deploy the backend code to a server. In order to successfully run on the server all of the files in the built folder needed to be synced as well as the entire node_modules folder.

If you’re reading this article you have probably seen the following meme before:

On some of my projects, the node_modules folder tallies up to over 700 MB. Even a fairly basic express app is 155.6 MB. Every deploy now requires uploading almost a full GB of data, for what surely amounts to much less actual code necessary.

Enter esbuild

esbuild is “An extremely fast JavaScript bundler”. You’re welcome to figure out how to bundle with webpack, but I have found esbuild to be unreasonably fast relative to webpack and a much simpler setup.

Add esbuild as a devDependency

yarn add --dev esbuild

Add the following to your package.json

{
  ...
  "scripts": {
    "start": "node built/index.js",
    "build": "esbuild index.ts --platform=node --bundle --minify --outfile=built/index.js"
  },
  ...
}

esbuild index.ts - tells the bundler that index.ts is the entry file to start bundling from. With just that, esbuild is able to determine what other files and libraries are imported.

–platform=node - This specifies that you are building for node and not the browser.

–bundle - Specifies that you want to output a single bundle file

–minify - Minifies the output JavaScript code

–outfile=built/index.js - Specifies what file to bundle into

You should now be able to run yarn build and see something like the below

yarn run v1.22.15
$ esbuild index.ts --platform=node --bundle --minify --outfile=built/index.js

  built/index.js  8.2mb ⚠️

Done in 0.21s.

Yes, you’re reading that correctly 0.21 seconds. From here you can run yarn start and the bundle will get loaded up and executed.

Deploying Your Bundle

I have now gone from a >150MB collection of thousands of files to a simple single file that needs to be copied over to my server. For most projects, deployment can be as simple as scp built/index.js username@xxx.xxx.xxx.xxx:~/project/built/index.js .

A Final Note and Benefit

I had been planning out bundling server side code for a while for the above reasons of simplifying the deployment process. I recently dove in to server side rendering for react (the React docs tell you next to nothing useful) and found this article that specifies you essentially need a bundler in order to import your React App component onto your server. This is a topic to be covered in a future post.