This project lets you watch a nock expression get processed step by step in a browser.
This project won't make any sense unless you know about nock. Nock is the virtual machine of Urbit. The complete spec fits on a page.
Nock-step is based on version 5 of the nock spec and uses the termimology from the reference materials of that time. As of Jan 2018 that version was superseded by version 4. Urbit.org has published both a clear explanation and detailed technical description of version 4.
Version 4 adds a few new operators and slightly modifies some of the more esoteric operators. The examples below use operators that did not change between versions.
The only user interface element at this time is the "Step" button. You specify the nock expression in the url. For example, an expression to increment the number 99 is [99 [4 0 1]]. So run the web page with the query string "?nock=[99 [4 0 1]]". Like this.
For the convenience of running directly out of github (using GitHub Pages), the repo contains bundle.js buit by browserify ux.js > bundle.js.