这里面 i 和 hobby 都是全局变量嘛
var hobby = document.getElementsByTagName("input");
for(i = 0;i < hobby.length;i++){
if(hobby[i].type == "checkbox"){
hobby[i].checked = true; }
}
}
function clearall(){
var hobby = document.getElementsByName("hobby");
for(i = 0;i < hobby.length;i++){
hobby[i].checked = false;}
}
