Illustrator scripting help. How to know if Live Effect applied?

Unfortunately @jonas_5930, we can't know if a Live Effect is applied. The scripting API only gives access to the very basic appearance (1 x fill, 1 x stroke).

You can do something hacky like this:

(function () {

    var doc = app.activeDocument,
        item = doc.selection[0];

    var expandedItem = expandAppearance(item.duplicate());

    /* 
    * now compare `item` with `expandedItem` somehow:
    * - different `typename`?
    * - number of paths or pathItems?
    * - different visibleBounds?
    * 
    * Example - a square with Live Effect Drop Shadow:
    *   `item` is a PathItem with 4 pathPoints
    *   `expandedItem` is a GroupItem containing:
    *      - a GrouptItem containing two PathItems, and
    *      - a RasterItem
    * 
    * So from this you can be sure that the square
    * does have some kind of special appearance.
    * I don't know how reliably you'd be able to tell
    * which Live Effect though.
    * 
    * Note: later you will delete `expandedItem`.
    */

    function expandAppearance(item) {
        app.redraw();
        app.executeMenuCommand('expandStyle');
        return app.activeDocument.selection[0];
    };

})();

Sometimes that can help. But otherwise, it isn't a good answer for you, sorry.

- Mark