subtraction using javascript
The below coding is my doubt. the total fees value is fetched from db. and paid is currently we enter. now i want that if i enter any value in paid, the entered value is subtract from db value and new value is display in bal fees text box and as well as store in db.
my coding is...
<HTML>
<HEAD>
<script language="javascript">
function doMath()
{
var oldbal= parseInt(document.getElementById('totalfees').value);
var paid= parseInt(document.getElementById('paid').value);
var totalfees = oldbal-paid;
document.getElementById('totalfees').value = totalfees;
}
</script>
</HEAD>
<body>
<?php
//fteching query
include("db.php");
$billtype_id = $_GET['billtype_id'];
$result=mysql_query("select * from bill_type where billtype_id=$billtype_id");
while($res=mysql_fetch_array($result))
{
$totalfees=$res['totalfees'];
}
//inserting query
$sql=mysql_query("insert into fees_admin values totalfees='$balfees' WHERE billtype_id='$billtype_id'",$conn);
include("config.php");
$balfees=$_POST['totalfees'];
$sql=mysql_query("insert into fees_admin values totalfees='$balfees' WHERE billtype_id='$billtype_id'",$conn);
?>
//html form
<form name="form" method="post" action="<?php $_SERVER['PHP_SELF'];?>">
<table>
<tr>
<td>Total Fees :</td>
<td><input name="total" type="text" id="oldbal" value="<?php echo $totalfees;?>开发者_JAVA百科" readonly="true" style="background-color:#FFFFFF"></td>
</tr>
<tr>
<td>Paid :</td>
<td><input type="text" id="paid" name="paid" onKeyUp="doMath();"></td>
</tr>
<tr>
<td>Bal Fees</td>
<td><input name="totalfees" type="text" id="totalfees" readonly="true" style="background-color:#FFFFFF"></td>
</tr>
</table>
</form>
Thanks for reading. please clear my doubt..
To be clear, input elements will return a string when you call "value". So in your example you would need to change the subtraction equation to:
var totalfees = parseFloat(oldbal) - parseFloat(paid);
You can use parseFloat to create a float from a string or parseInt if you don't need decimal precision.
You should probably also change you HTML code to make the DOM level 0 event "change" rather than keyUp. Its more consistent across a range of different browsers (Desktop, Mobile, Tablet).
Change
var oldbal= parseInt(document.getElementById('totalfees').value);
to
var oldbal = parseInt(document.getElementById('oldbal').value);
Function should then look like
function doMath()
{
var oldbal = document.getElementById('oldbal').value;
var paid = document.getElementById('paid').value;
var totalfees = parseInt(oldbal) - parseInt(paid);
document.getElementById('totalfees').value = totalfees;
}
I believe you were retrieving the wrong input element.
加载中,请稍侯......
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