ASP中控制文本框的隐藏和出现

<input type="text" id="mytext">
  
 <input type="button" value="显示" οnclick="javascript:document.getElementByIdx('mytext').style.visibility='visible';">
  
 <input type="button" value="隐藏" οnclick="javascript:document.getElementByIdx('mytext').style.visibility='hidden';">