Get Selected Radio Button/Check Box

Many times you will want to be able to get the selected radio button and/or check box in a browser environment. For the radio button, you will want to check the value and perform some task. Or, you will want to verify that one radio button has been selected. For check boxes, you may want to see which ones are selected or you could want to check that at least one is selected. Here's a couple of functions that work with radio buttons and check boxes. These are set up to be generic, so they can be reusable.

function getSelectedRadio(buttonGroup) {
   // returns the array number of the selected radio button or -1 if no button is selected
   if (buttonGroup[0]) { // if the button group is an array (one button is not an array)
      for (var i=0; i<buttonGroup.length; i++) {
         if (buttonGroup[i].checked) {
            return i
         }
      }
   } else {
      if (buttonGroup.checked) { return 0; } // if the one button is checked, return zero
   }
   // if we get to this point, no radio button is selected
   return -1;
} // Ends the "getSelectedRadio" function

function getSelectedRadioValue(buttonGroup) {
   // returns the value of the selected radio button or "" if no button is selected
   var i = getSelectedRadio(buttonGroup);
   if (i == -1) {
      return "";
   } else {
      if (buttonGroup[i]) { // Make sure the button group is an array (not just one button)
         return buttonGroup[i].value;
      } else { // The button group is just the one button, and it is checked
         return buttonGroup.value;
      }
   }
} // Ends the "getSelectedRadioValue" function

function getSelectedCheckbox(buttonGroup) {
   // Go through all the check boxes. return an array of all the ones
   // that are selected (their position numbers). if no boxes were checked,
   // returned array will be empty (length will be zero)
   var retArr = new Array();
   var lastElement = 0;
   if (buttonGroup[0]) { // if the button group is an array (one check box is not an array)
      for (var i=0; i<buttonGroup.length; i++) {
         if (buttonGroup[i].checked) {
            retArr.length = lastElement;
            retArr[lastElement] = i;
            lastElement++;
         }
      }
   } else { // There is only one check box (it's not an array)
      if (buttonGroup.checked) { // if the one check box is checked
         retArr.length = lastElement;
         retArr[lastElement] = 0; // return zero as the only array value
      }
   }
   return retArr;
} // Ends the "getSelectedCheckbox" function

function getSelectedCheckboxValue(buttonGroup) {
   // return an array of values selected in the check box group. if no boxes
   // were checked, returned array will be empty (length will be zero)
   var retArr = new Array(); // set up empty array for the return values
   var selectedItems = getSelectedCheckbox(buttonGroup);
   if (selectedItems.length != 0) { // if there was something selected
      retArr.length = selectedItems.length;
      for (var i=0; i<selectedItems.length; i++) {
         if (buttonGroup[selectedItems[i]]) { // Make sure it's an array
            retArr[i] = buttonGroup[selectedItems[i]].value;
         } else { // It's not an array (there's just one check box and it's selected)
            retArr[i] = buttonGroup.value;// return that value
         }
      }
   }
   return retArr;
} // Ends the "getSelectedCheckBoxValue" function

To use one of these functions, just make a call and pass the radio button or check box object. For example, if you want to find out if at least one check box is selected and the check box field name is MyCheckBox, then write the following statements:

var checkBoxArr = getSelectedCheckbox(document.forms[0].MyCheckBox);
if (checkBoxArr.length == 0) { alert("No check boxes selected"); }