I have two JSON objects in Javascript, identical except for the numerical values. It looks like this:
var data = {
\"eth0\":{\"Tx\":\"4136675\",\"Rx\":\"13
Maybe it's already answered enough, but let me add my shameless plug :) A JSON (actually any javascript object or array structure) diff & patch library I open sourced at github:
https://github.com/benjamine/jsondiffpatch
it generates diffs (also in JSON format, and with a small footprint), which you can use client (check the test page) & server side, and if present, it uses http://code.google.com/p/google-diff-match-patch/ for long strings automatically.
check the DEMO page to see how it works.