Dynamicly change SelectOneRadio value in java script function -- Please hel

Question

Hello, I need to change SelectOneRadio value within a javascript function. But it doesn't seem to work for me. Can someone tall me what I did wrong or how to get this?
Thanks a lot!
I have :
<h:panelGrid Columns="3">
<h:selectOneRadio id="myRadio", value="#{myBean.radioOption}" />
     <f:selectItems value="#{myBean.radioOptionList}" />
</h:selectOneRadio>
</h:panelGrid>
<script >
function needToChangeRadioValue(choice){
if ( choice == something ) { 
     document.getElementById("myForm:myRadio").value="1"; //doesn't really work
     document.getElementById("myForm:myRadio").immediate="true";
} else if ( choice == somethingelse ) {
     document.getElementById("myForm:myRadio").value="2"; //doesn't really work
     document.getElementById("myForm:myRadio").immediate="true";
} else {
     document.getElementById("myForm:myRadio").value="3"; //doesn't really work
     document.getElementById("myForm:myRadio").immediate="true";
</script>
-- java --
ArrayList radioOptionList;
public ArrayList getRadioOptionList(){
     radioOptionList = new ArrayList();
     radioOptionList.put("1","Option1");
     radioOptionList.put("2","Option2");
     radioOptionList.put("3","Option3");
     return radioOptionList;
}

Answer 1

Thank you for the quick response!
Does it work for you? I tryed getElementsByName("myform:myRadio")[1].value="1"; No errors but the screen doesn't show that radio button is "on". I also created another function to go through the form object and try to set the attribute but no luck. From screen, I still don't see the option is selected(or on). I have :
<script .... >
function checkRadioButton(){
var allElem = document.forms['myform'].elements;
for ( i=0 ; i< allElem.length; i++ ){
alert("element name = " + allElem.name ); // I see myform:myRadio three times
alert("element id = " + allElem[i].id ) // when name="myform:myRadio, id is null/empty
alert("element value = "+ allElem[i].value ); // when name="myform:myRadio, value = 1, 2, 3 respectively
if ( allElem[i].name == 'myform.myRadio' ) {
     var attributes = allElem[i].attributes;
for ( j =0; j < attributes.length; j++) {
          if ( attributes[j].name == 'CHECKED' ) { // I found CHECKED is one of selectOneRadio's attributes
               if ( i == 1) {
     attributes[j].value = true; // It still doesn't work. I didn't see that option1 get selected/on.
What I am trying to do is common, I think !!?? Really appreciate your help.