As an alternative to XML, many Ajax developers prefer to use JSON, available at http://www.json.org. JSON is a lightweight data-interchange format that is based on a subset of the JavaScript language. Because it is a subset of JavaScript, we can very easily convert a JSON response into something that the receiving script can consume directly.
For example, we may return the following, which is a valid JSON array:
["value1","value2","value3","value4"]
Or we might return a JSON object literal such as this:
{"today": "Wednesday", "planet" : "Earth" , "mood" : "happy" }
If this were found in the responseText property of an XHR object, we might quickly make it available for use via this:
var result = eval(xhr.responseText);
And now you would be able to reference the individual values in the result object, like so:
var str = "Today is " + result.today + " and on planet "+ result.planet + " people
are generally " + result.mood;