<input type = checkbox name= a value = a1>a1
<input type = checkbox name= a value = b1 checked>b1
<input type = checkbox name= a value = c1 checked>c1
<input type = checkbox name= a value = d1>d1
<script>
function check()
{
aa= document.getElementsByName('a');
for (i=0;i<aa.length;i++)
{
if (aa[i].checked == false)
alert(aa[i].value+'没有选中');
}
}
check();
</script>
<input type = checkbox name= a value = a1>a1
<input type = checkbox name= a value = b1 checked>b1
<input type = checkbox name= a value = c1 checked>c1
<input type = checkbox name= a value = d1>d1
<script>
function check()
{
aa= document.getElementsByName('a');
for (i=0;i<aa.length;i++)
{
if (aa[i].checked == false)
alert(aa[i].value+'没有选中');
}
}
check();
</script>
function Button1_onclick() {
var ObjectCount=0
var j=0
ObjectCount=document.all.length;
var ifcheck=0
for (i=1;i<ObjectCount;i++)
{
if (document.all.item(i).tagName=="INPUT")
if (document.all.item(i).type=="checkbox")
if (document.all.item(i).checked)
ifcheck=1;
}
if (ifcheck==0 )
alert("请选择一个选项!");
}