JS-to-Java bridge should be well documented. Part of the javadoc will be pushed as part of RT-19917, then it will have to be updated to:
Discuss primitive type mapping, then JSObject.
Note that Node objects also extend JSObject.
Discussion of JSObject.
Use of setMember to bind Java object to JavaScript properties.
Mapping Java values to JavaScript
Note this applies to setMember; the parameters of JSObject#call; and the result of in Javascript calling methods (or accesng) fields of Java object (next section?).