var n=0;
var a = document.getElementsByName("fee1[]");
for(var i=0; i<a.length; i++)
{
if(!isNaN(a.value)) n += parseFloat(a.value);
}
var a = document.getElementsByName("fee2[]");
for(var i=0; i<a.length; i++)
{
if(!isNaN(a.value)) n += parseFloat(a.value);
}
document.getElementsByName("fee")[0].value = n==0 ? "" : n;
var a = document.getElementsByName("fee1[]");
for(var i=0; i<a.length; i++)
{
if(!isNaN(a.value)) n += parseFloat(a.value);
}
var a = document.getElementsByName("fee2[]");
for(var i=0; i<a.length; i++)
{
if(!isNaN(a.value)) n += parseFloat(a.value);
}
document.getElementsByName("fee")[0].value = n==0 ? "" : n;
<input name="fee1[]"><input name="fee2[]">
<input name="fee1[]"><input name="fee2[]">
<input name="fee">
<input type="button" value="累加" onclick="sum()">
<script>
function sum()
{
o = document.getElementsByTagName("INPUT");
total = 0;
for(c=0;c<o.length;c++)
{
if(/^fee[0-9]+\[\]$/.test(o[c].name))
{
if(o[c].value!="") total+=parseInt(o[c].value);
}
}
document.getElementsByName("fee")[0].value = total;
}
</script>