Javascript: JQuery DatePicker, Chrome and MAXLENGTH

Having just spent 2 hours swearing violently at my computer, I thought I'd share this little bug tracking story...

I am writing a simple data entry page that contains a couple of date fields, for which I'm using the very nice JQuery UI datepickers.

I have used them all over the place with no problems at all, however on this page I was getting some weird behaviour when the submit button was clicked:

1. If the date fields were empty, the form submitted fine.
2. But if a date had been selected, when you clicked submit, the date picker for the first populated date field popped up and the form did not submit.

Some testing revealed this only happened in Chrome - my version of which is the v6 beta release.

An update to the JQuery UI did not fix the problem.

Some debugging code revealed that on submit, the datepicker fields were being focussed - so as far as the datepicker code was concerned, it was working correctly.

However, the object inspector in Chrome showed no unwanted event listeners that could be doing this.

Some more swearing, a minimal test case and a comparison with a working page later revealed the problem - the MAXLENGTH attribute had been set, in a copy/paste debacle, to 8 - clearly too short for a dd/mm/yyyy date.

So, presumably, Chrome allows you to set content longer than the MAXLENGTH from script, but then will not let you submit the form, instead focussing the offending field - it makes perfect sense when you think about it, really.

Firefox and IE both allow you to submit the form with the longer data - although you can make an argument for that making sense too. I don't know what the W3C say on this issue.

JS: Client side templating

I originally created this for an autocomplete widget I needed for a project ages ago; eventually it became too annoying to write all the code for the millions of conditions so I just used the YUI one instead, which is a pain in the arse to set up but works perfectly when you've done it.

Anyway, while looking around at existing solutions, they all seemed to have the problem that the markup was either fixed and styled with CSS, or generated in a callback. Neither of these solutions was ideal; the first results in a widget usable most of the time but very uncustomisable for more unusual uses, and the second is very designer unfriendly if you need to separate your coding and design teams.

So, my idea was to be able to write your HTML as normal, then mark an element as a template container. This template would contain databound variables. It would be removed from the DOM on page load, stored, then repeatedly generated for each item in a provided dataset.

Basically, it is inspired by the ASP.NET repeater control, .NET being my primary development environment.

I recently refactored the code to be more generally useful, and created a jQuery plugin wrapper that enables it to be used using the jQuery selectors and AJAX functionality.

It has uses beyond autocomplete, of course; any AJAXian updatable areas could use it.

Pros and cons are:

• Keeps the template HTML in the same file as everything else; this can be a pro if the area is specific to a certain page or you are using a "master page" or "header / footer includes" style design, and a con if the template is to be used in several places. In that case you are probably better off with a server-side templating system to generate the HTML and dumping that in using the jQuery native functions.
• Allows lightweight data transfer; instead of returning all of the HTML you can just return a JSON dataset.

The basic template code and the jQuery wrapper can be downloaded from the links below:

tiny_template_base.js
jquery.htemplate.js

Usage:

First of all, you need a datasource, which will be an array of objects, for example:

[
 {id:1, name:'Alice'},
 {id:2, name:'Bob'},
 {id:3, name:'Carol'}
]

Then, you need to set up the template:

<ul id="testTemplate">
    <li class="@ItemClass">@Text</li>
</ul>

Note the SQL style variable placeholders. When the template is created with the ID of the <ul> element the <li> will be cleared. It is then reproduced for every item in the data array.

Note: EVERYTHING contained within the template element is treated as the data row, so you can have very complex repeating templates; as a very simple example you could have two list items for every data item should you want to. This is more useful for creating table based templates.

The actual call to populate the template looks like this:

// Call using local data and the simple unwrappered template code
var template = new HTemplates.Template('testTemplate');
template.populate(data);

// Call using the jQuery wrapper and an AJAX data source
$('#testTemplate').hTemplate();     
$('#testTemplate').hTemplate().populate(data);

You can download an example page plus an example JSON datasource from the links below:

template_example_ajax.html
template_example.html

Note: You will need the jQuery framework; it has been tested with 1.4. You will also need to change the script paths to match your setup.

The jQuery plugin is the first time I have looked at jQuery; I'm not 100% sure this is the best way to create a plugin; the hTemplate().populate() call looks odd to me. Also there is probably a better way of JSON parsing that is less fragile than my check-for-open-bracket-then-eval() method.