try the following (didn't test, so there might be errors):
<form id=form1>
......
</form><script language="javascript">
function form1.onsubmit()
{var n = 6;
var count = 0;var elements = this.elements;
for (var i=0; i < elements.length; i++)
{
if (elements[i].type == "checkbox" && elements[i].checked)
count++;
}if (count == 0)
{
alert("还没有选");
return false;
}
else if (count < n)
{
alert("not enough");
return false;
}
else if (count > n)
{
alert("too many");
return false;
}}
</script>
<form id=form1>
......
</form><script language="javascript">
function form1.onsubmit()
{var n = 6;
var count = 0;var elements = this.elements;
for (var i=0; i < elements.length; i++)
{
if (elements[i].type == "checkbox" && elements[i].checked)
count++;
}if (count == 0)
{
alert("还没有选");
return false;
}
else if (count < n)
{
alert("not enough");
return false;
}
else if (count > n)
{
alert("too many");
return false;
}}
</script>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=checkbox>
<input type=submit>
</form><script language="javascript">
function form1.onsubmit()
{var n = 6;
var count = 0;var elements = this.elements;
for (var i=0; i < elements.length; i++)
{
if (elements[i].type == "checkbox" && elements[i].checked)
count++;
}if (count == 0)
{
alert("还没有选");
return false;
}
else if (count < n)
{
alert("not enough");
return false;
}
else if (count > n)
{
alert("too many");
return false;
}alert("submitting");}document.write(new Date());
</script>
for(var i = 0 ; i < 50 ; i++){
document.write("<input type='checkbox' name='checkName' value='" + i + "'>");
}
document.write("<input type=submit value='submit'></form>");function doSubmit(){
var items = getSelectedCheckBoxByName("checkName");
var count = items.length;
var message = "" ;
var ok = false ;
if(count == 0)
message = "还没有选";
else if(count < 6)
message = "还没有选够";
else if(count > 6)
message = "选多了";
else
ok = true;
if(!ok)
alert(message);
return ok;
}
/*****************************************************************
Name getSelectedCheckBox
Purpose 取选择的checkBox对象,并将该值保存到数组中,返回该数组
Date 2004-1-17
Param items Array对象数组
Return Array
*****************************************************************/
function getSelectedCheckBox(items){
var values = new Array();
if(items != null)
for(var i = 0 ; i < items.length ; i++)
if(items[i].checked)
values.push(items[i].value);
return values;
}/*****************************************************************
Name getSelectedCheckBoxByName
Purpose 取选择的checkBox对象,并将该值保存到数组中,返回该数组
Date 2004-1-17
Param itemName checkBox对象名称
Return Array
*****************************************************************/
function getSelectedCheckBoxByName(itemName){
var items = document.getElementsByName(itemName) ;
return getSelectedCheckBox(items);
}