Is it possible to only obtain the columnsPositions(cp) of the page where the frame is located?

Hey dublove,

I'm not sure what is your intend in knowing the column position of a textframe, but here is what I would do.
Note that there is a script ou there (I can fetch it if you're interested in it) that applies an object style to the whole story based on the one applied on the selected textframe. As usual, we can easily tweak it if needed.

The property .marginPreferences.columnsPositions is a page property. Hence, it will give you information regarding the page settings, not the actual selected frame. You can however get the location of the selected textFrame and compare it with the settings of the page. Create then an alert that shows you what you want.

That brings another issue. Coordinates in Indesign can be a bit messy, especially if you use millimeters (like me). I found it helpful rounding up the numbers.

The code could then be like this

// =========================== Function Round decimals  ============================
function RoundWithDecimal(number, decimals){
    var multiplier = Math.pow(10,decimals);
    return Math.round(number*multiplier)/multiplier;
}

// ================================ Main Function  ==================================
function main() {
    if (app.selection.length === 0 || !(app.selection[0] instanceof TextFrame)) {
        alert("Please select a text frame.");
        return;
    }
    
    var selectedTf = app.selection[0];
    var selectedFrameX = RoundWithDecimal(selectedTf.geometricBounds[1], 2); // x1 coordinate in mm, rounded to 2 decimals
    
    if (selectedFrameX === 20) {
        alert("Position = Column 1");
    } else if (selectedFrameX === 109) {
        alert("Position = Column 2");
    } else {
        alert("X position: " + selectedFrameX + " mm");
    }
}

main();