Rename visible layers in Illustrator

gistfile1.txt

var doc = app.activeDocument;
var prefix = Window.prompt ("Rename prefix", "", "By Sharkbox");

function transverseTree(layer){    
    if( layer.visible ){
    	layer.name = prefix + "-" + layer.name;
    }
    
    for( var i=0; i<layer.layers.length; i++){
       transverseTree( layer.layers[i] );
    }
 }

if( prefix != null){
    for( var i=0; i<doc.layers.length; i++){
        transverseTree( doc.layers[i] );
    }
}