change field value when select radio buttons

Question

I want to change the value of hidden input field when radio buttons selected :

    <input type="radio" name="r1" value="10" />10
    <br/>
    <input type="radio" name="r1" value="45" />45
    <br/>
    <input type="hidden" name="sum" value="" />

for example when user click on one the buttons the value of hidden field change to that value.

Answer 1

Use the onClick property:

<input type="radio" name="r1" value="10" onClick="document.getElementById('hidfield').value=this.value"/>10
    <br/>
    <input type="radio" name="r1" value="45" onClick="document.getElementById('hidfield').value=this.value"/>
    45
    <br/>
    <input type="hidden" name="sum" value="" id="hidfield" />

Answer 2

You can try for example

<input type="radio" id="radio1r1" name="r1" value="10" />10
<br/>
<input type="radio" id="radio2r1" name="r1" value="45" />45
<br/>
<input type="hidden" name="sum" value="" />

jQuery("input[id^='radio']").click(function() {
    jQuery("input[name='sum']").val(jQuery(this).val());
}

So then when user click on each radio we handle it by various id with same start.

Answer 3

Using jQuery it would be:

$(":radio").click(function () {
    var inputValue = $this.val();
    $(":hidden[name='sum']").val() = inputValue;
$(":hidden[name='sum']").name() = "lalala";
    });

I've not double checked that code so it might need a little tweaking.