Source JS Minifier [WIP]

A CLI tool to download source code of a webpage from a URL(validated), then fix relative URLs, then minify the css stylesheets in-place, then replace in-place or concatenate its JS scripts with the minified script, & then open the resultant webpage in browser.

Implemented in NodeJS. [Demonstration Project]

Install

From npm registry: npm install source-js-minifier

Run locally

1. Download source code
2. npm install from repo
3. Run Command

node src/app.js minify <url>

node src/app.js minify <url> --custom => To use custom js minifier

node src/app.js minify <url> --concatenate => To concatenate all js scripts (including downloaded) into one & attach minified version at the end of html body.

node src/app.js minify <url> --css => To perform in-place css minification.

node src/app.js minify <url> --custom --concatenate --css => Use all together

Note:

• Files will be saved to ./output/

Dependencies:

• Commander: CLI tool
• Downloading files: node-fetch
• JS Minifier: terser
• HTML Parser, manipulator, generator: parse5-utils
• For cross platform file opening in browser: open
• CSS minifier: clean-css

For Custom Minifier:

• JS Parser: acorn
• JS manipulator: recast
• JS Generator: astring

Custom Minifier

An attempt to develop a custom js minifier.

Functionalities to be developed:

1. Remove whitespaces ---------------------- done
2. Remove comments ------------------------- done
3. Switch to shorthand syntax -------------- done
4. Resolve constant expressions ------------ done
5. Concatenate/Bundle scripts -------------- done
6. Rename identifiers etc [TODO:]
7. Remove unused variables & dead code [TODO:]
8. if else to terenary --------------------- done
9. assignment operator --------------------- done

Steps req:

1. Parsing js code in AST
2. AST tree traversal using recursion
3. For each node perform modifications using Visitor Pattern
4. Code re-generation

For exploring AST: https://astexplorer.net/

For more info on using AST: https://youtu.be/C06MohLG_3s

Extremenly helpful guide on AST manipulation: https://lihautan.com/manipulating-ast-with-javascript/

Note:

• Concepts Required: Abstract Syntax Trees of HTML & JS, DFS traversal, Visitor Pattern, Synchronous code in NodeJS
• ASTs has been extensively used because it best server the purpose.

TODOs

1. Static type check, Lint, Comments, Best practices/conventions, Logging
2. Write tests / unit tests
3. More optimizations in Custom Minifier
4. REFACTOR needed
5. Relook error-handling & synchronization