SpiderMonkey build (Firefox's JavaScript engine). You can find a prebuilt version here: https://download-origin.cdn.mozilla.net/pub/firefox/nightly/latest-mozilla-central/.
Atlernatively you can build it from source: https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Build_Documentation.
Download the source code: https://github.com/binast/binjs-ref and build a local version.
make encode: encode JavaScript filesmake test: run benchmarks