How to set gradient/pattern by name to the default Fill?

[Flowgun]

Hello everyone,
I'm trying to write a script that changes the default fill content. It is pretty straightforward for RGBColor and CMYKColor (and NONE), but I'm finding difficulty finding a way to place a gradient or a fill by name (they exist in the swatches so a if there's a way to set a swatch to the fill can be a solution.

[Flowgun · Accepted solution]

this worked

    var doc = app.activeDocument;
    var tmp = doc.pathItems.add();
    tmp.setEntirePath([[0,0],[0,0]]);
    tmp.filled = true;
    var sw = doc.swatches.getByName(patternName);
    tmp.fillColor = sw.color;
    doc.defaultFilled = true;
    doc.defaultFillColor = tmp.fillColor;
    tmp.remove();