@Naftule - with "defiant.js", it is possible to query a JSON structure with XPath expressions. Check out this evaluator to get an idea of how it works:
http://www.defiantjs.com/#xpath_evaluator
Unlike JSONPath, "defiant.js" delivers the full-scale support of the query syntax - of XPath on JSON structures.
The source code of defiant.js can be found here:
https://github.com/hbi99/defiant.js