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Mini Web Compiler

Compiles JavaScript code and SCSS stylesheets for the web, in a simple and clean GUI for Windows.

This application manages project files stored in JSON format. Each project you manage with Mini Web Compiler needs a separate miniwebcompiler.json file in its root directory. It specifies the project’s name, a few options and most importantly the source files to compile. You can create or add such project files in the Mini Web Compiler application and they are active until you remove them. The application runs in the background and once it detects that one of these files (or the files they reference) has changed, it starts compiling the file according to its type and the project options.

The following file types are supported:

  • CSS: Minify
  • JavaScript: Bundle, minify
  • SCSS: Compile to CSS, minify

Most of the actual processing and compilation is done by widely recognised and established tools. All of them are made available as NPM packages that run on Node.js. They are bundled together in a managing GUI that calls the tools with the appropriate parameters and takes care of the necessary file handling to ensure proper source maps (which are fully maintained along all the way) and keep important source comments like license summaries.

These are the tools that do the work:

All these tools are included in the setup package. They are installed locally in the application directory so they won’t interfer with any globally installed NPM packages/tools. The actual versions can be seen in the application’s About dialog.

Note: There was support to transpile JavaScript files to ECMAScript 5 in previous versions of Mini Web Compiler. This was only needed to target Internet Explorer, which has been abandoned by Microsoft now. To read more about this feature, download version 1.4.0 and also switch this page to the tag v1.4.0 and read this again.

JavaScript configuration

JavaScript files are run through rollup to bundle them into a single file, if any imports of other files are detected in the source file. The bundled code is wrapped into an immediately invoked function expression (IIFE). The parameters of that function and the arguments when calling it can be specified with comment lines like /* iife-params($) */ and /* iife-args(jQuery) */ near the top of the file. The code between the parentheses is inserted into the generated file. The comment /* no-iife */ disables the use of an IIFE and basically concatenates all the files together. The comment /* no-bundle-suffix */ avoids adding the ".bundle.js" suffix to the bundled file name. This is only effective when a different build output directory is specified (see below).

JavaScript mangling by uglify-js can be configured with the following comments: /* no-mangle */ disables mangling completely (nothing is renamed), /* keep-fnames */ disables renaming functions, /* keep-fargs */ disables renaming function arguments (parameter names). These options can be used together with the “Unminify” command to debug compressing or mangling errors in your JavaScript code. It will take the .min.js file and beautify it into a .unmin.js file in the same (output) directory.

The build output files can be written to a separate directory to keep your source code folder tidy. Use a comment like /* build-dir(...) */ and anything in the parentheses is the relative path to your build output files. The build directory is created if it doesn’t exist. This configuration also works for CSS files, but note that you cannot use relative url() references without manually copying the build file to the correct directory.


This is how it looks like in a JavaScript source files:

/*! frontfire-core.js v2.0.0-dev | @license MIT | */
/* build-dir(build) */

// Copyright (c) 2022, Yves Goergen,
// (More of the license text)

"Source code here...";

And here is a bundling example that merges several JavaScript files into a single output file:

/*! frontfire-core-singlefile.js v2.0.0-dev | @license MIT | */
/* no-iife */
/* build-dir(build) */

// Copyright (c) 2022, Yves Goergen,
// (More of the license text)

import "./arraylist";
import "./frontfire-core";
import "./color";
import "./datacolor";

Script automation

If the file miniwebcompiler.cmd exists in the project directory (next to miniwebcompiler.json), then it will be called after each file was compiled (except if unchanged, but still when clicking the Compile all button). It will be passed the name of the compiled source file (as listed in the project with its relative path) as first argument.

This script can be used to perform additional steps after a compiled file was updated, like post-processing with external tools or copying it into other project directories conveniently.


Here’s what I do with these scripts:

@echo off
if "%~1" == "ui\src\css\frontfire-ui-complete.scss" (
	echo Copying frontfire-ui-complete.min.css to my website
	copy /y ui\src\css\build\frontfire-ui-complete.min.css* C:\Web\mywebsite\lib\frontfire2 >nul
	echo Copying frontfire-ui-complete.min.css to Farbeimer
	copy /y ui\src\css\build\frontfire-ui-complete.min.css* C:\Web\farbeimer\lib\frontfire2 >nul
if "%~1" == "ui\src\js\frontfire-ui-complete-singlefile.js" (
	echo Copying frontfire-ui-complete-singlefile.min.js to my website
	copy /y ui\src\js\build\frontfire-ui-complete-singlefile.min.js* C:\Web\mywebsite\lib\frontfire2 >nul
	echo Copying frontfire-ui-complete-singlefile.min.js to Farbeimer
	copy /y ui\src\js\build\frontfire-ui-complete-singlefile.min.js* C:\Web\farbeimer\lib\frontfire2 >nul

System requirements

  • Windows 7, 8, 10, 11 (64-bit) (currently only tested in Windows 10)
  • .NET Framework 4.8 or later (comes with Windows Update)
  • No Node.js (included in the setup package)
  • No other tools (included in the setup package)


Please go to the releases section of this repository to find the latest installation package. It extracts all files into a directory in your user profile (no administrator privileges used) and sets up the start menu and autostart shortcuts.

Build prerequisites

These steps must be taken to use the application from source code and build the setup package. The setup will pick up the files from their global installation path. This means that globally installing the npm packages is required on the build machine, but the installed application will always use its own embedded versions of the tools.

Note: None of this applies when installing Mini Web Compiler from the setup package.

  • Install Node.js for Windows from
  • Install csso: npm install csso-cli -g
  • Install rollup: npm install rollup -g
  • Install rollup-plugin-sourcemaps: npm install rollup-plugin-sourcemaps -g
  • Install uglify-es: npm install uglify-js -g
  • Install sass: npm install sass -g

To upgrade all tools to the latest version, run: npm update -g


MIT license

See Setup/LICENSE-3RD-PARTY.txt for licenses of third-party tools that are included in the setup package.