How to check if TextFrame is being used as a mask in the clipping group

I thought of something else, 

check for textItem fillColor and strokeColor, both should be [NoColor] if they’re the clipping path

you may have to cycle through all pathItems and compoundPathItems, check for clipping property and if there’s none, then you would assume the clipping path is a textItem, hopping there’s only one

Good catch — yes, that's possible. The snippet relies on Illustrator's guarantee that the mask is the topmost object at the moment the clipping mask is created (Illustrator moves it there automatically). Once you manually reorder the group's contents, that assumption no longer holds. If you're reordering via script, keep your own reference to the mask object before moving it. And in the Layers panel, the mask is always the item labeled “<Clipping Path>” — that's the reliable visual check regardless of order.

You're right that TextFrame doesn't expose a clipping property — only PathItem and CompoundPathItem do.

The reliable way is to check the group itself: a clip group has its clipped property set to true, and the clipping mask is always the topmost object in the group (Adobe Help: "The first object in a layer or group becomes the clipping mask"). Since Illustrator orders pageItems from back to front, the mask is the last item:

var g = app.activeDocument.groupItems.getByName("your group");

if (g.clipped) {

    var maskItem = g.pageItems[g.pageItems.length - 1];

    if (maskItem.typename === "TextFrame") {

        // this TextFrame is the clipping mask

    }

}

This works for any pageItem type used as a mask — TextFrame included — because you identify it by its position in the group rather than a type-specific property.

Reference: https://helpx.adobe.com/illustrator/desktop/manage-objects/edit-objects/about-clipping-masks.html