如何累加网页中两个文本框的值？

[tommyking]

有三个文本框
<input type="text" name="txt_amount1" size="60" onkeyup="javascript:caculate();">

<input type="text" name="txt_amount2" size="60" onkeyup="javascript:caculate();">

<input type="text" name="txt_total_amount" size="60" >

function caculate()
{
var amount1,amount2;
amount1=form1.txt_amount1.value;
amount2=form1.txt_amount2.value;
form1.txt_total_amount.value=txt_amount1和txt_amount2值的总和
“=后的表达式怎么写”
}

谢谢回复

[awaysrain]

function caculate()
{
var amount1,amount2;
amount1=form1.txt_amount1.value;
amount2=form1.txt_amount2.value;
form1.txt_total_amount.value= parseFloat(amount1) + parseFloat(amount2)
}

[seabell]

form1.txt_total_amount.value=parseFloat(amount1)+parseFloat(amount2)

[awaysrain]

加了判断

<SCRIPT LANGUAGE=JAVASCRIPT>
function caculate()
{
var amount1,amount2;
amount1=parseFloat(form1.txt_amount1.value);
amount2=parseFloat(form1.txt_amount2.value);
if(isNaN(amount1))
amount1=0
if(isNaN(amount2))
amount2=0

form1.txt_total_amount.value= amount1 + amount2
}
</SCRIPT>
<FORM name=form1>
<input type="text" name="txt_amount1" size="60" onkeyup="javascript:caculate();">

<input type="text" name="txt_amount2" size="60" onkeyup="javascript:caculate();">

<input type="text" name="txt_total_amount" size="60" >
</FORM>

[zhaoweiwei]

<input type="text" name="txt_amount1" size="60" onkeyup="javascript:caculate();">

<input type="text" name="txt_amount2" size="60" onkeyup="javascript:caculate();">

<input type="text" name="txt_total_amount" size="60" >

function caculate()
{
var amount1,amount2;
amount1=parseFloat(form1.txt_amount1.value);
amount2=parseFloat(form1.txt_amount2.value);
form1.txt_total_amount.value=txt_amount1+txt_amount2

}