<html><head><title>New Page 1</title>
</head><body onload="alert(f1.d1.length)"><form name=f1 method="POST" action="">
<p><select size="1" name="d1">
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
<option>5</option>
</select></p>
</form></body></html>
</head><body onload="alert(f1.d1.length)"><form name=f1 method="POST" action="">
<p><select size="1" name="d1">
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
<option>5</option>
</select></p>
</form></body></html>
f1.d1.options.length
<input type="button" onclick="getLength()">
<select id="s1" size="4" multiple>
<option value="a">a</option>
<option value="b">b</option>
<option value="c">c</option>
<option value="d">d</option>
</select>
<script>
function getLength(){
var s = s1.innerHTML;
alert((s.length - s.replace(/selected/gi,"").length) / 8)
}
</script>
var q=new Array();
for(t=0;t<selectID.length;t++)
if(selectID.options[t].selected)q[q.length]=t;;alert("有"+q.length+"各被选中;序号依次为"+q.toString());
你用的是M-select吧
那就只能用循环了