The following properties of the model are all null.

${model.parent}
${model.root}
${model.content}
${model.root}
${model.definition}

According to jsimak, it should be "easy" to add them.
If possible, please enable these very handy properties in JavaScript model context too.

Because JavaScriptRenderingModel is treated as JS object in freemarker, all method calls are now routed to the model#call method.

We can add simple conditions to treat methods above as special cases.