未定義変数の等価チェック

/**
 * Copyright yprops ( http://wonderfl.net/user/yprops )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/xKwB
 */

package {
    import flash.text.TextField;
    import flash.display.Sprite;
    import flash.utils.getQualifiedClassName;
    public class FlashTest extends Sprite {
        private var tf :TextField;
        public function FlashTest() {
            var vInt :int;
            var vUint :uint;
            var vNum :Number;
            var vBool :Boolean;
            var vStr :String;
            var vObj :Object;
            var vUdf :*;
            
            settx("////未定義の変数の等価チェック////");
            addtx("int", vInt);
            addtx("uint", vUint);
            addtx("Number", vNum);
            addtx("Boolean", vBool);
            addtx("String", vStr);
            addtx("Object", vObj);
            addtx("*", vUdf);
            addtx("null", null);
            addtx("undefined", undefined);
            addtx("\"\"", "");
        }
        
        //----------------
        
        private function settx(caption :String) :void{
            tf = new TextField();
            tf.width = 300;
            tf.height = 400;
            tf.background = true;
            tf.border = true;
            tf.appendText(caption + "\n");
            addChild(tf);
        }
        private function addtx(caption :String, val :*) :void{
            var cn :String = getQualifiedClassName(val);
            var ts :String;
            try{ ts = val.toString(); }catch(er :Error){ts = "[errored]";}
            tf.appendText(
                "[" + caption + "]" +
                "\n\tclassname\t\t" + cn +
                "\n\tvalue\t\t\t" + val +
                "\n\ttoString()\t\t" + ts +
                "\n\t== true\t\t\t" + (val == true) +
                "\n\t=== true\t\t" + (val === true) +
                "\n\t== \"\"\t\t\t" + (val == "") +
                "\n\t=== \"\"\t\t\t" + (val === "") +
                "\n\t== null\t\t\t" + (val == null)+
                "\n\t=== null\t\t" + (val === null)+
                "\n\t== undefined\t" + (val == undefined) +
                "\n\t=== undefined\t" + (val === undefined) +
                "\n\t== 0\t\t\t" + (val == 0)+
                "\n\t=== 0\t\t\t" + (val === 0)+
                "\n\n"
            );
        }
    }
}