The default Custom Plugin script that comes with Sketch

Sketch Custom Plugin - Default

log('This is an example Sketch script.');

var documentName = context.document.displayName();
log('The current document is named: ' + documentName);

var selectedLayers = context.selection;
var selectedCount = selectedLayers.count();

if (selectedCount == 0) {
	log('No layers are selected.');
} else {
	log('Selected layers:');
	for (var i = 0; i < selectedCount; i++) {
		var layer = selectedLayers[i];
		log((i + 1) + '. ' + layer.name());
	}
};