#target Photoshop

var docRef = app.activeDocument;
var activeLayer = docRef.activeLayer;

if (activeLayer.kind == "LayerKind.TEXT") {
    var fontPostScriptName = app.fonts.getByName(activeLayer.textItem.font).postScriptName
    alert(fontPostScriptName);
} else {
    alert("テキストレイヤーを選択して下さい。");
}