エラーの検出にはJavaScriptに標準で用意されている alert() が使えます。

// main.js
enchant();
window.onload = preloadAssets;
 
var game;
var scene;
var sprite;
 
function preloadAssets()
{
	game = new Game(320,480);
	game.onload = init;
 
	game.preload("images/chara1.png");
 
	game.start();
}
 
function init()
{
	game.scale = 1;
	game.fps = 30;
	scene = new Scene();
	scene.backgroundColor = "#000";
	game.pushScene(scene);
 
	sprite = new Sprite(32, 32);
 
	sprite.image = game.assets["images/chara1.png"];
 
	sprite.backgroundColor = "#66F";
	sprite.x = 128;
	sprite.y = 128;
 
	scene.addChild(sprite);
 
	main();
}
 
function main()
{
	game.addEventListener(Event.UP_BUTTON_DOWN, moveFrame);
	game.addEventListener(Event.DOWN_BUTTON_DOWN, moveFrame);
	game.addEventListener(Event.RIGHT_BUTTON_DOWN ,moveFrame);
	game.addEventListener(Event.LEFT_BUTTON_DOWN, moveFrame);
}
 
function moveFrame(e)
{
	switch (e.type)
	{
	case Event.UP_BUTTON_DOWN:		sprite.y--;		break;
	case Event.DOWN_BUTTON_DOWN:		sprite.y++;		break;
	case Event.RIGHT_BUTTON_DOWN:		sprite.x++;		break;
	default:
		{
			alert("ERROR\n EVENT TYPE : " + e.type );
		}
		break;
	}
}

enchantjs_error_handle.zip