LINQ to XML for JavaScript uses the same approach for good perf as LINQ to XML for .NET – atomization. Read more: http://openxmldeveloper.org/home2/bm8qcmjy/public_html/blog/b/openxmldeveloper/archive/2012/10/24/linq-to-xml-for-javascript-gaining-performance-through-atomization.aspx
I’ve been hard at work in my spare time for months now developing a small JavaScript library that enables you to write code in the style of LINQ to XML. I developed this because I needed to implement some interesting functionality in JavaScript, and I already basically had the code written in C#, so writing this library enabled me to translate that C# code to JavaScript with a minimum of fuss and trouble. ltxml.js – LINQ to XML for JavaScript