The article combined Javascript and JSON, but they aren't really the same. Javascript is the programming, JSON is the data.
JSON is JavaScript Object Notation, a data representation language that is much less complex than XML. Developers are migrating to it because it doesn't take as many resources to parse a JSON object, compared to XML. If you are dealing with millions of messages, you can save a lot of CPU time with JSON.
You can easily convert JSON to XML, but not necessarily the other way around. But even when they represent the same data, they are just two ways to express it.
Save CPU time? Bwahahaha! Today’s twerps don’t care about resources. They write code that eats memory, bandwidth, and disk space like it’s free.