my pretty code

 function discountcardchange(cardSelectControlName,cardSelectChangeValue, cardInputControlName) {

     ///<summary>

     ///span show/hidden

     ///2009-04-15

     ///</summary>

     ///<parame name="" type=""> "sltdiscountcard" / "null" /"spndiscountcard"</parame>

     ///<returns type=""></returns

     //1.null

     if(!document.getElementById) return;

     var cardSelectControl = document.getElementById(cardSelectControlName);

     var cardInputControl = document.getElementById(cardInputControlName);

     if ((!cardSelectControl) || (!cardInputControl)) return;

     //2.change

     cardSelectControl.value === cardSelectChangeValue ?

     cardInputControl.style.display = "none" :

     cardInputControl.style.display = "block";

 }