Toolchain engines

There are two engines available by default for Asciidoctor.js. The first is an Opal-based engine and the second is the new pure JavaScript engine. If you apply the org.asciidoctor.js plugin you get a toolchain called asciidoctorjs which is the pure JavaScript engine and a toolchain called asciidoctorjs3 which is the Opal engine.

Note than not all formatters support all engines. It is therefore important that both engines exist in order to give authors of the various packages on NPM to port their backends and extensions to support the 4.0+ package of @asciidoctorjs/core.