[devote]

<form onsubmit="return test();">
<label><input type="checkbox">Согласен</label><br>
<label><input type="radio" name="A" value="Da" />Да</label><br>
<label><input type="radio" name="A" value="Net" />Нет</label><br>
<select>
<option>1</option>
<option>2</option>
<option>3</option>
</select><br>
<input type="submit" value="Enter">
</form>
<script>
    function test() {
        var chk = document.querySelector('input[type="checkbox"]'),
            radio = document.querySelector('input[type="radio"]:checked'),
            sel = document.querySelector('select');

        alert( "Checkbox checked: " + chk.checked );
        alert( "Radio checked: " + ( radio ? radio.value : "Не выбран" ) );
        alert( "Select selected: " + sel.value );

        return false;
    }
</script>