increment form field value

[decbrad]

Hi all... just a quick question! I have a standard form field that gets filled from a database when the page loads... all good so far! What I would like to do is allow the users to increment this value by adding a plus and minus each side.

Here's my hacked effort so far... ;o(

<script type="text/javascript">
function add() {
document.getElementById('input').value=document.getElementById('input').value + .1;
}

function subtract() {
document.getElementById('input').value=document.getElementById('input').value - .1;
}
</script>

<form>
Value:
<input type="button" onClick="subtract();" value="-" name="button">
<input type="text" name="input" value="18.3" id="input" size="5" maxlength="4">
<input type="button" onClick="add();" value="+" name="button2">
</form>

It seems to work when subtracting but not when adding? If anybody can point me in the right diection, or even to an online tutorial, i'd seriously appreciate it!

Thanks in advance

Decbrad

[penders]

Because '+' is also used for string concatenation, and JS assumes that the contents of form fields are strings, things can at times not turn out as expected... If you tell JS that the .value is a number (ie. convert it with parseFloat()) then it should be OK...

document.getElementById('input').value = parseFloat(document.getElementById('input').value) + .1;

<edit>

Just noticed another (recent) related thread which may help...
[webmasterworld.com...]

[decbrad]

Thanks a million Penders... that worked a treat;o)

rgds,
Decbrad