convert $().data('someKey') to a json object if possible.

[LeoYuan]

Note: it might not be a bug, just make some improvement for data()

improvement description

now, the data() is using attr() internally which has no process to convert the result, even if the result is a json-like string.

how to reproduce?

html

<div id="test" data-x='{"c": 2, "d": [1, 2, 3], "e": {x: 1}}'></div>

js

console.log(af('#test').data('x'));

how to do?

try to convert the result to a json object if possible, otherwise return the original result.