The benefit of JSON on other formats is that it is recognized natively by JavaScript. This is huge advantage because you don’t need to write a code for parsing an XML document to extract the data and get it throught the net. So it saves time and it is faster.

The JSON format is very simple:

{
  "menu": "File",
  "commands": [
      {
          "title": "New",
          "action":"CreateDoc"
      },
      {
          "title": "Open",
          "action": "OpenDoc"
      },
      {
          "title": "Close",
          "action": "CloseDoc"
      }
   ]
}

and you use the eval() JavaScript function to  parse it.
var req = new XMLHttpRequest();
req.open("GET", "file.json", true);
req.onreadystatechange = myCode;   // the handler
req.send(null);
The JavaScript handler:
function myCode()
{
   if (req.readyState == 4)
   {
        var doc = eval('(' + req.responseText + ')');
   }
}