Creating a flexicontent plugin with jquery or mootools

The doplgact is the way to place your code inside a function of the FLEXIcontent field , e.g. inside image.php for image field.

Thus you can use the URL i have given you above to call the function "mydata()" inside the FLEXIcontent field.

You create JSON output as you need ...........

For passing parameters to function "mydata()" just add variable to the URL
and retrieve it via
$varx = JRequest:getVar('varx');

Regards