<input name=a1 onblur="b.value=a1.value*1+a2.value*1+a3.value*1">+
<input name=a2 onblur="b.value=a1.value*1+a2.value*1+a3.value*1">+
<input name=a3 onblur="b.value=a1.value*1+a2.value*1+a3.value*1">=
<input name=b readonly>
<input name=a2 onblur="b.value=a1.value*1+a2.value*1+a3.value*1">+
<input name=a3 onblur="b.value=a1.value*1+a2.value*1+a3.value*1">=
<input name=b readonly>
</head><body>
<input type=text name="t1">
<input type=text name="t2">
<input type=text name="t3">
<input type=text name="result" readonly onclick="this.value=parseFloat(t1.value)+parseFloat(t2.value)+parseFloat(t3.value)">
</body></html>
最后得到结果<html><head>
<script>
function add()
{
var sum=0
var a=document.getElementsByName("t1")
for(var i=0;i<a.length-1;i++)
{
sum=parseFloat(a[i].value)+sum
}
f1.result.value=sum
}
</script>
</head><body>
<form name=f1>
<input type=text name="t1">
<input type=text name="t1">
<input type=text name="t1">
<input type=text name="t1">
<input type=text name="t1">
<input type=text name="result" readonly onclick="add()">
</form>
</body></html>