โปรแกรมคิดค่าไฟ

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

package {
    import flash.events.Event;
    import flash.text.TextFieldType;
    import flash.text.TextField;
    import flash.display.Sprite;
    
    public class FlashTest extends Sprite {
        
        
        private var input:TextField;
        private var output:TextField;
        public function FlashTest() {
             var label:TextField = new TextField();
            addChild( label );
            label.text = "Input Unit";
            label.y = 80;
            
            input = new TextField();
            addChild( input);
            input.border = true;
            input.text = "0";
            input.height = 30;
            input.type = TextFieldType.INPUT;
            input.y = 95;
            input.addEventListener(Event.CHANGE , onChange );
        
           output = new TextField();
           addChild(output);
           output.y = 150;
           
        }
        private function onChange(e:Event):void{
            
            if( isNaN(Number(input.text)) ){
                output.text = "not a number";
            }else{
                output.text = cal(Number(input.text)).toString(); 
            }
        }
        private function cal( unit:uint ):Number{
            var price:int = 0;
            //first 10 Unit
            if( unit > 10 ){
                price = 10*10;
                unit -= 10;
            }else{
                price = unit*10;
                return price;
            }
            //20 Unit
            if( unit > 10 ){
                price = 15*20;
                unit -= 10;
            }else{
                price = unit*15;
                return price;
            }
            //More
            price +=  unit*20;
            return price;
        }

    }
}