Click the button to select the gender and interests

<input type = "button" value = " modify gender" the above mentioned id = "btn14"> 
        <input type = "radio" name = "sex" value = "1"> M
         <input type = "radio" name = "sex" value = "2" id = " rad1"> M
         <Script type = "text / JavaScript">
             function My $ (ID) {
                 return document.getElementById (ID); 
            } 
            // rule: in the form tag, and if the property only one value, and the value of this property is itself 
            // (for example, a radio button is selected by default: the checked = "the checked") 
            // so, write js code, DOM operation, when the property value is a Boolean type on it 
            my $ ( "btn14").onclick = function() {
                my$("rad1").checked = true;
            };
        </script>
        <br />
        
        <input type="button" value="选择兴趣" id="btn15" />
        <input type="checkbox" name="xingqu" value="1" />吃饭
        <input type="checkbox" name="xingqu" value="2" id="a"/>睡觉
        <input type="checkbox" name="xingqu" value="3" />打豆豆
        <input type="checkbox" name="xingqu" value="4" id="b"/>唱歌
        <script type="text/javascript">
            my$("btn15").onclick =function(){
                my$("a").checked=true;
                my$("b").checked=true;
            };
        </script>