UglifyJS

It also contains tools that allow one to automate working with JavaScript code:
- A parser which produces an abstract syntax tree (AST) from JavaScript code.
- A code generator which outputs JavaScript code from an AST, also providing the option to get a source map.
- A compressor (optimizer) — it uses the transformer API to optimize an AST into a smaller one.
- A mangler — reduce names of local variables to (usually) single-letters.
- A scope analyzer, which is a tool that augments the AST with information about where variables are defined/referenced etc.
- A tree walker — a simple API allowing you to do something on every node in the AST.
- A tree transformer — another API intended to transform the tree.