Supporting package to compile JS and CSS in Express applications

Usage no npm install needed!

<script type="module">
  import expressCompile from '';



express-compile is middleware that compiles JS and CSS on the fly within your express application. This project is based off electron-compile project and uses the same compilers.

For JavaScript:

  • JavaScript ES6/ES7 (via Babel)
  • TypeScript
  • CoffeeScript

For CSS:

  • LESS
  • Sass/SCSS


  • Jade


  • CSON

How does it work? (Slightly Harder Way)

Put this at the top of your Express app:

import {Compiler} from 'express-compile';

    root: '.',
    cwd: 'public',
    paths: ['public/**/*'],
    ignore: ['public/node_modules/**/*'],
    ignoreStyleCache: true

I did it, now what?

From then on, you can now simply include files directly in your HTML, no need for cross-compilation:

  <script src=""></script>
  <link rel="stylesheet" href="main.less" />

or just require them in:

require('./mylib')   // mylib.ts

Something isn't working / I'm getting weird errors

express-compile uses the debug module, set the DEBUG environment variable to debug what express-compile is doing:

## Debug just express-compile
DEBUG=express-compile:* npm start

## Grab everything except for Babel which is very noisy
DEBUG=*,-babel npm start

How do I set up (Babel / LESS / whatever) the way I want?

If you've got a .babelrc and that's all you want to customize, you can simply use it directly. express-compile will respect it, even the environment-specific settings. If you want to customize other compilers, use a .compilerc file. Here's an example:

  "application/javascript": {
    "presets": ["stage-0", "es2015", "react"],
    "sourceMaps": "inline"
  "text/less": {
    "dumpLineNumbers": "comments"

.compilerc also accepts environments with the same syntax as .babelrc:

  "env": {
    "development": {
      "application/javascript": {
        "presets": ["stage-0", "es2015", "react"],
        "sourceMaps": "inline"
      "text/less": {
        "dumpLineNumbers": "comments"
    "production": {
      "application/javascript": {
        "presets": ["stage-0", "es2015", "react"],
        "sourceMaps": "none"

The opening Object is a list of MIME Types, and options passed to the compiler implementation. These parameters are documented here:

How can I precompile my code for release-time?

express-compile comes with a command-line application to pre-create a cache for you.

Usage: express-compile --appDir [root-app-dir] paths...

  -a, --appdir  The top-level application directory (i.e. where your
                package.json is)
  -v, --verbose  Print verbose information
  -h, --help     Show help

Run express-compile on all of your application assets, even if they aren't strictly code (i.e. your static assets like PNGs). express-compile will recursively walk the given directories.

express-compile --appDir /path/to/my/app ./src ./static