[thelist] Javascript orderform speed issue

Matt Warden mwarden at gmail.com
Sun Mar 5 03:12:57 CST 2006

Hash: SHA1

Rory Lysaght wrote:
> I've got a large order form that uses script to update the subtotal
> automatically as soon as you enter a quantity.  The page itself is
> pretty large - about 1050 products in about 11 tables.  I'm working on
> slimming down that code.  But the problem I have is the speed of
> updating the page subtotal.  Every time someone enters a number in the
> quantity field, I need to loop through all 1050 fields to update the
> page total.  In Firefox it's really zippy, but in IE6/Win it's
> incredibly slow.  I'm guessing on older /slower PCs it's almost
> unusable.  I've optimized the Javascript as much as I can, but I'm
> wondering if anyone can explain why it's radically slower in IE, or
> suggest a faster way to do this?
> You can see the form here:   http://memoryboxco.com/orderform.htm

There's no need to go through every field. Only the ones the user has

Something like...

var touched = {};

window.onload = function()
	var inputs = document.getElementsByTagName('input');
	for (var i=0; i<inputs.length; i++) {
		inputs[i].onchange = markTouched;

function markTouched(e)
	e = e || window.event;
	var input = e.srcElement || e.target;
	var id = input.id;
	touched[id] = input.value;

function updateTotal()
	var totalinput  = ...;
	// ...
	// use the object touched = {id: value, id: value, etc.}
	// to calculate total. you don't really need to revisit
	// the actual input fields at this point.
	// ...

window.setInterval("updateTotal();", 800);

- --
Matt Warden
Miami University
Oxford, OH, USA

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