Nothing came close to the speed of XSLT when IE was ruling.
I loved it, and enabled us to build very fast web apps.
But then came JSON, Firefox and other browsers that made XSLT/XML look a less supported and ageing tech.
I tried to write a js equivalent in 2008. And after a couple of iterations it finally ended up with this: http://gitHub.com/pure/pure
It is declarative. With CSS selectors instead of XPATH. Do not mix at all with HTML. And fast rendering.
Syntax is verbose, but felt that the power was worth it. Never found a declarative, functional way to do the same kind of transforms on JSON data, but I'm sure it must exist by now.