JavaScript Minifier

A powerful command-line utility written in Go to minify JavaScript files. This tool uses no external dependencies and relies solely on Go's standard library for minification.

Features

• Removes comments (both single-line and multi-line)
• Removes unnecessary whitespace and newlines
• Removes spaces around operators and punctuation
• Variable name shortening (optional)
• Directory processing with parallel execution
• Watch mode for automatic minification
• Preservation of license comments (optional)
• JSON output format for statistics
• No external dependencies

Installation

1. Make sure you have Go installed on your system
2. Clone this repository
3. Build the binary:

go build -o js-minifier

Usage

Basic Usage

Minify a single file (creates .min.js):

./js-minifier -input script.js

Specify custom output file:

./js-minifier -input script.js -output custom.min.js

Advanced Features

Process all JavaScript files in a directory:

./js-minifier -input ./src

Watch directory for changes:

./js-minifier -input ./src -watch

Enable variable name shortening:

./js-minifier -input script.js -shorten-vars

Preserve license comments:

./js-minifier -input script.js -preserve-license

Output statistics in JSON format:

./js-minifier -input script.js -json

Command Line Options

• -input: Input JavaScript file or directory (required)
• -output: Output file path (optional, default: [input].min.js)
• -watch: Watch mode - monitor directory for changes
• -preserve-license: Preserve license comments
• -shorten-vars: Enable variable name shortening
• -json: Output statistics in JSON format

Minification Rules

The tool applies the following minification rules:

1. Removes all single-line comments (// ...)
2. Removes all multi-line comments (/* ... */)
3. Preserves license comments (/*! ... */) when -preserve-license is enabled
4. Removes extra whitespace and newlines
5. Removes spaces around operators (+, -, *, /, =, etc.)
6. Removes unnecessary semicolons
7. Removes spaces after function keywords
8. Removes spaces around brackets and parentheses
9. Shortens variable names (when -shorten-vars is enabled)

Examples

Basic Minification

Input file (script.js):

function calculateSum(a, b) {
    // This is a comment
    const result = a + b;
    return result;
}

Output file (script.min.js):

function calculateSum(a,b){const result=a+b;return result;}

With Variable Shortening

Using -shorten-vars flag:

function calculateSum(a,b){const c=a+b;return c;}

Processing a Directory

Process all .js files in src directory:

./js-minifier -input ./src -shorten-vars

This will create minified versions of all JavaScript files:

• src/file1.js → src/file1.min.js
• src/file2.js → src/file2.min.js

Watch Mode

Monitor directory for changes:

./js-minifier -input ./src -watch -preserve-license

This will:

• Watch the src directory for changes
• Automatically minify modified files
• Preserve license comments
• Show real-time statistics

Performance

The minifier typically achieves:

• 40-50% size reduction on standard JavaScript files
• 60-70% reduction with variable name shortening
• Parallel processing for directory operations
• Millisecond-level processing time for most files