A complete Test & Benchmark Suite is included for your perusal.
You may also read through the annotated source code.
Underscore is an open-source component of DocumentCloud.
Downloads (Right-click, and use “Save As”)
|Development Version (1.3.3)||37kb, Uncompressed with Plentiful Comments|
|Production Version (1.3.3)||4kb, Minified and Gzipped|