var tf:TextField = new TextField();
			tf.autoSize = TextFieldAutoSize.LEFT;
			tf.border = true;
			addChild(tf);
			tf.x = 200;
			tf.y = 200;
			tf.multiline = true;
			tf.height = 200;
			
			tf.appendText("params:" + "\n");
			try {
				var keyStr:String;
				var valueStr:String;
				var paramObj:Object = LoaderInfo(this.root.loaderInfo).parameters;
				for (keyStr in paramObj) {
					valueStr = String(paramObj[keyStr]);
					trace(this, "flashVars->", keyStr, valueStr);
					tf.appendText("\t" + keyStr + ":\t" + valueStr + "\n");
				}
			} catch (error:Error) {
				tf.appendText(error.toString());
			}

For FlashVars testing on screen

Writing FlashVars to TextField

ActionScript 3