onchange事件
<input type="text" name="A" onchange="doSum()">
<input type="text" name="B" onchange="doSum()">
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<input type="text" name="total"><script>
function doSum(){]
var sum = parseFloat(form.A.value) + parseFloat(form.B.value) ;
form.total.value = sum;
}
<script>
<input type="text" name="A" onchange="doSum()">
<input type="text" name="B" onchange="doSum()">
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<input type="text" name="total"><script>
function doSum(){]
var sum = parseFloat(form.A.value) + parseFloat(form.B.value) ;
form.total.value = sum;
}
<script>
function test(){
str3.value=Math.floor(str1.value)+Math.floor(str2.value);}
</script>
<input type="text" name="str1" value="5" onkeyup="test()"><br>
<input type="text" name="str2" onkeyup="test()"><br>
<input type="text" name="str3">
<script>
test();
</script>
function sum()
{
var num1,num2;
if(document.all.txtNum1.value == "")
num1 = 0;
else
num1 = document.all.txtNum1.value;
if(document.all.txtNum2.value == "")
num2 = 0;
else
num2 = document.all.txtNum2.value;
document.all.txtSum.value = parseInt(num1) + parseInt(num2);
}
function checkWithKeyCode()
{
if(!(event.keyCode<=57 && event.keyCode>=48))
{
event.keyCode = 0;
}
}
</SCRIPT>
<BODY>
sum:<INPUT type="text" name="txtSum" readonly="true"><br><br>
num1:<INPUT type="text" name="txtNum1" onpropertychange="sum()" onKeyPress="checkWithKeyCode(this);"><br><br>
num2:<INPUT type="text" name="txtNum2" onpropertychange="sum()" onKeyPress="checkWithKeyCode(this);"><br><br>
</BODY>
<head>
<script>
function doSum(){
var num1,num2;
num1 = document.all.A.value!=""?document.all.A.value:0;
num2 = document.all.B.value!=""?document.all.B.value:0;
if (isNaN(parseFloat(num1)) || isNaN(parseFloat(num2)) ) {
alert('请输入数字！');
return false;
}
var sum = parseFloat(num1) + parseFloat(num2) ;
document.all.total.value = sum;
}
</script>
</head>
<body>
<form>
分数A<input type="text" name="A" id=A onkeyup="return doSum()"><br>
分数B<input type="text" name="B" id=B onkeyup="return doSum()"><br>
总和:<input type="text" name="total" readonly>
</form>
</body>
</html>