BTW, you can also start from the top right with the two 1s. One of the rightmost two cells contains a mine, so the 3rd from the right can't.
1. Even though there are newer XSLT standards, XSLT 1.0 is still dominant. It is quite limited and weird compared to the newer standards.
2. Resolving performance problems of XSLT templates is hell. XSLT is a Turing-complete functional-style language, with performance very much abstracted away. There are XSLT templates that worked fine for most documents, but then one document came in with a ~100 row table and it blew up. Turns out that the template that processed the table is O(N^2) or worse, without any obvious way to optimize it (it might even have an XPath on each row that itself is O(N) or worse). I don't exactly know how it manifested, but as I recall the document was processed by XSLT for more than 7 minutes.
JS might have other problems, but not being able to resolve algorithmic complexity issues is not one of them.