清除按鈕功能

不需要被清除的field
clearDefault="初始值" 或 <script type="text/javascript">form1.fieldName.clearDefault="初始值";</script>
清除按鈕 onclick="clearValue();"

function clearValue(){
 for(var i=0; i<document.forms[0].elements.length; i++){
  obj = document.forms[0].elements[i];
  if("field_Q" == obj.className){
   if( undefined == obj.clearDefault ){
    if("text" == obj.type) {
     obj.value = "";
    } else if("checkbox" == obj.type) {
     obj.checked = false;
    } else if("radio" == obj.type) {
     obj.checked = false;
    } else if("select" == obj.type) {
     obj.selectedIndex = 0;
    }
   } else {
    if("text" == obj.type) {
      obj.value = obj.clearDefault;
    } else if("checkbox" == obj.type) {
     if(obj.value == obj.clearDefault) obj.checked = true;
    } else if("radio" == obj.type) {
     if(obj.value == obj.clearDefault) obj.checked = true;
    } else if("select" == obj.type) {
     obj.options.value = obj.clearDefault;
    }
   }
  }
 }
}