Create frame in Illustrator with js

Hi @Yuliascript, you are on the right track! Here's a version that does each of things you want. Please look through each part and compare to your script and see what I've done differently.

- Mark

/**
 * @author m1b
 * @discussion https://community.adobe.com/t5/illustrator-discussions/create-frame-in-illustrator-with-js/m-p/14441605
 */
(function () {

    var myDoc = app.activeDocument;

    // get (or make) the layer
    var myLayer,
        layerName = "GUIDES";
    try {
        myLayer = myDoc.layers.getByName(layerName);
    } catch (error) {
        myLayer = myDoc.layers.add();
        myLayer.name = layerName;
    }

    // make the black color
    var myBlack = new CMYKColor();
    myBlack.black = 100;
    myBlack.cyan = 0;
    myBlack.magenta = 0;
    myBlack.yellow = 0;

    // make a rectangle the size of the first artboard
    var bounds = myDoc.artboards[0].artboardRect;
    var myTrimLine = myLayer.pathItems.rectangle(bounds[1], bounds[0], bounds[2] - bounds[0], -(bounds[3] - bounds[1])); // TLWH

    // set the rectangle's properties
    myTrimLine.filled = false;
    myTrimLine.stroked = true;
    myTrimLine.strokeWidth = 0.5;
    myTrimLine.strokeColor = myBlack;
    myTrimLine.strokeOverprint = true;

})();