These pages are old. They apply to UglifyJS v2. Version 3 has evolved a lot in the mean time to support most of ES6. Please check the documentation in the official repository for up-to-date information. Big thanks to all contributors, especially to Alex Lam S.L., who has maintained this project for years!
UglifyJS — the name mangler
UglifyJS can reduce names of local variables and functions usually to single-letters. That's a safe optimization provided the following stand:
- You don't directly call the global eval function.
- You don't use the
- You don't access the
UglifyJS can detect the first two cases and it will disable the mangler
automatically in code areas that are poisoned by usage of eval
with. UglifyJS cannot detect if you're using the
function's name property, however; in such code the mangler
can potentially break your code. For example
the JADE template engine is affected
by this issue (coupled with its
author “I am the
smartest and know what's best” attitude).
ast = UglifyJS.parse(code); ast.figure_out_scope(); ast.compute_char_frequency(); ast.mangle_names(); code = ast.print_to_string();
That's all there is to it. Make sure to call figure_out_scope() first, then call mangle_names() on the toplevel node. Optionally insert the compute_char_frequency() there to get names that are optimized for GZip compression (names will be generated using the most frequent characters first).
If you also compress your code, then you want to mangle names after compression, since the compressor might drop unused identifiers, unreachable code etc. The full sequence would be this:
ast = UglifyJS.parse(code); // compressor needs figure_out_scope too ast.figure_out_scope(); compressor = UglifyJS.Compressor() ast = ast.transform(compressor); // need to figure out scope again so mangler works optimally ast.figure_out_scope(); ast.compute_char_frequency(); ast.mangle_names(); // get Ugly code back :) code = ast.print_to_string();
JS compressor of world fame.Open demo
- Code generator
- The AST structure
- SpiderMonkey AST
- Scope analysis
- AST walker
- AST transformer
- UglifyJS on Github
Latest blog entries tagged "uglifyjs"
- Using UglifyJS for code refactoring
- Should you switch to UglifyJS2?
- UglifyJS online demo
- UglifyJS — why not switching to SpiderMonkey AST
/** May the source-map be with you! **/