三个单选题每题必须选一个答案的表单特...|太原网站建设|太原做网站|太原网站优化|太原黑马网络工作室

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>Error</title>
</head>
<body>
<form id="form1" name="form1" method="post" action="" onsubmit="return false;">
第一题:
<input name="a1" type="radio" value="" />
<input name="a1" type="radio" value="" />
<input name="a1" type="radio" value="" /><br />
第三题:
<input name="a2" type="radio" value="" />
<input name="a2" type="radio" value="" />
<input name="a2" type="radio" value="" /><br />
第四题:
<input name="a3" type="radio" value="" />
<input name="a3" type="radio" value="" />
<input name="a3" type="radio" value="" />
<br />
<label>
<input type="submit" name="button" id="button" value="提交"/>
</label>
</form>
<script>
function checkRadio(l){
  for(var i=l.length;i--;){
    if(l[i].checked){
      return l[i].value;
    }
  }
  return false;
}
document.getElementById("button").onclick=function(){
  var a= document.getElementsByName("a1");
  if(!checkRadio(a)){
    alert("第一题没选");
  }
  a= document.getElementsByName("a2");
  if(!checkRadio(a)){
    alert("第二题没选");
  }
  a= document.getElementsByName("a3");
  if(!checkRadio(a)){
    alert("第三题没选");
  }
}
</script>
</body>
</html>