Christian Heilmann

Posts Tagged ‘javascript’

The new web development challenge – independent modules in larger frameworks

Wednesday, March 5th, 2008

I just wrote a post on the YDN Developer blog how our work as web developers is very likely to change in the nearer future. I am not talking about the imminent coming of IE8 and its – thankfully – standard new rendering engine but about web architectural decisions I have witnessed in lots of talks with large corporations, big web sites and people that try to move their products into backend frameworks.

The new challenge is that the page as we know it will be very likely to die out soon and be replaced with a set of modules that can be customized for the user needs and by what we know of them or even opened up to third party developers. The success of the likes of facebook and the new MySpace developer framework are very likely to be just the start. A shame that the technologies and standards we use to develop clean and maintainable web products are not geared towards that kind of approach. Where is the cascade if everything should be self-contained?

Most common JavaScript mistakes – Paul Boag grilled me for the Boagworld Podcast

Wednesday, February 27th, 2008

One of the biggest podcasts in the UK when it comes to web development and web design is Paul Boag’s Boagworld.com. Every week Paul talks about what’s hot and happening in the development world and mixes it with good humour and believable insights.

This week’s podcast is entitled “Hiring” but ends with an interview Paul did with me over Skype on Valentine’s. If you listen to it, you’ll hear that I did have a cold and it was a long day, and if you read the transcript, you’ll see that both Paul and me “um…” a lot.

Nevertheless Paul had some very good questions, and I hope I had interesting answers.

GeekUp Leeds talk about the YUI right when the new version (2.5) is out!

Wednesday, February 20th, 2008

I am right now sitting on the National Express train back from Leeds, UK heading for home and just finished a talk at GeekUp about the YUI and JavaScript. The slides are available on slideshare:

The GeekUp people also filmed the presentation and the long Q&A session, and I will try to get my hands on these recordings to see what I actually said as the 3 hour stint with 2.5 hour train rides was confusing.

Nevertheless I had a great time, got rid of the Schwag I didn’t want to carry back home and had some really good questions in the Q&A session. If you live in the north of the UK, make sure to check out GeekUp

Also make sure to check out the new 2.5 release of the YUI and the official blog post about it.

The great implementer swindle – making badge use easy doesn’t make it clever!

Tuesday, February 12th, 2008

No matter how you’ll turn it – the future of web design will not revolve around pages and sites but around modules. The social web and the systems providing canvasses to put up applications and badges is here and will be here to stay.
This is cool as it puts the end user much more in control of their own experience. However it is also bad as it means the standards we tried to set up and follow in the last, err 9 years are rapidly going down the drain.

The main reason is the promise of “quick wins” and “low hanging fruit” and once again the attempt to use technology to make the web a WYSIWYG and drag and drop interface.

Here’s my latest find that made me wonder why we don’t learn from errors of the past – making things easy to implement is not the same as making them easy to use!

Consider the job to be to offer third parties a chance to add a badge to their site. Not hard at all – the main task is really on the implementation level, i.e. making sure the styles of the parent side don’t clobber the badge.

Easy to implement badges

Now, to make it easy for the implementers, here’s the proposal:



Implementers can choose the size and the skin in attributes and give a brand name to display. This is pretty easy to understand and the script to make it work is no voodoo either:


(badge = function(){
var s = document.getElementsByTagName(‘script’);
for(var i=0;s[i];i++){
if(s[i].getAttribute(‘src’) 'badge.js'){
var div = document.createElement('div');
var content = s[i].firstChild.nodeValue;
div.innerHTML = '

Awesome badge!

';
div.appendChild(document.createTextNode(content));
var size = s[i].getAttribute('size');
var skin = s[i].getAttribute('skin');
var col,width;
switch(size){
case 'small':width = 100;break;
case 'large':width = 400;break;
default:width = 200;break;
}

switch(skin){
case 'blue':col = '#ccf';break;
case 'green':col = '#cfc';break;
default:col = '#ccc';break;
}

div.style.background = col;
div.style.width = width + 'px';
s[i].parentNode.replaceChild(div,s[i]);
}

}
})();

You loop through all script elements, compare the src with yours, read the attributes and the element content, assemble a badge, set the visual style and replace the script with the badge.

This makes implementation a breeze and allows the implementer even to choose the size and colour for each badge they use.

However there are several problems with this:

Invalid HTML

You cannot add custom attributes to HTML nilly-willy as it makes your HTML invalid. This is a tough one to make people understand as HTML validation is considered a nice-to-have than a real necessity. Years of lax browsers have made us immune to that issue. And, actually you could work around that with a custom DTD!

If you wondered if adding a src and content in the SCRIPT is invalid HTML - it isn’t. All the recommendations say is that user agents should ignore what is in the SCRIPT when there is a src attribute:

The script may be defined within the contents of the SCRIPT element or in an external file. If the src attribute is not set, user agents must interpret the contents of the element as the script. If the src has a URI value, user agents must ignore the element’s contents and retrieve the script via the URI. Note that the charset attribute refers to the character encoding of the script designated by the src attribute; it does not concern the content of the SCRIPT element.

Poor Performance.

This way of adding a badge loads the badge.js file for every instance. While it may be cached this is still an unnecessary overhead. The other issue is that every SCRIPT element makes the browser stop rendering until the script inside it or the one it links to with the src attribute is executed.

The more scripts you have in your document body, the slower your site will be! I can safely say that most of my firefox crashes are because of third party JS includes (really: ads). As a real badge implementation would do more HTTP calls – most of the time directly after rendering – this would add even more overhead.

Bad Accessibility and SEO

Non-JavaScript clients (like search robots) will not find anything with this kind of badge. Screen readers might get the badge but the replacement of a script after calling itself must be hard to stomach for any engine that ties into the browser’s DOM.

Alternative proposals

All of the following proposals here do require more of the implementer, but also make sure that none of the above problems occur. Using progressive enhancement we change a valid HTML structure that can be indexed by search spiders and end up with the same result.

All solutions work with one script include – in this case at the end of the document, but with an onload tweak this could also be in the head. This means the HTTP overhead is much less and your script does not get hit hard by every implementation.

Full-on progressive enhancement with a server-side fallback

This solution simply uses links to a proper backend solution that’ll offer a landing page for each brand. This means proper SEO as the links can be followed and the landing page becomes a starting point. The properties of the badge are URL parameters. While not all of them must be used by the server-side fallback they still can. You can never have too much data.





The script is not hard:


(fpebadge = function(){
var divs = document.getElementsByTagName(‘div’);
var b = [];
for(var i=0;divs[i];i++){
if(divs[i].className.indexOf(‘fpebadge’) ! -1){
b.push(divs[i]);
}

}
for(var i=0;b[i];i++){
var link = b[i].getElementsByTagName(‘a’)[0];
if(link){
var urldata = link.getAttribute(‘href’);
var badgecfg = convertURL(urldata);
var div = buildBadge(badgecfg);
if(div){
b[i].parentNode.replaceChild(div,b[i]);
}

}
}

function buildBadge(badgecfg){
if(badgecfg){
var div = document.createElement(‘div’);
div.innerHTML = ‘

Awesome badge!

‘;
if(badgecfg.brand){
div.appendChild(document.createTextNode(badgecfg.brand));
}

var col,width;
switch(badgecfg.size){
case ‘small’:width = 100;break;
case ‘large’:width = 400;break;
default:width = 200;break;
}

switch(badgecfg.skin){
case ‘blue’:col = ‘#ccf’;break;
case ‘green’: col = ‘#cfc’;break;
default:col = ‘#ccc’;break;
}

div.style.background = col;
div.style.width = width + ‘px’;
return div;
}

}
function convertURL(urldata){
if(urldata.indexOf(‘?’)!==-1){
var chunks = urldata.split(‘?’)[1].split(‘&’);
var badgecfg = {};
for(var i=0,j=chunks.length;i var vp = chunks[j].split(‘=’);
badgecfg[vp[0]] = vp[1];
}

}
return badgecfg;
}

})();

Progressive enhancement with a server-side landing page

If you don’t want to provide a branded landing page, but just have the name displayed and if you don’t trust your implementers to be able to properly encode ampersands :) then you can also just have a landing page and keep the badge properties in class names:




The code is not much different:


(pebadge = function(){
var divs = document.getElementsByTagName(‘div’);
var b = [];
for(var i=0;divs[i];i++){
if(divs[i].className.indexOf(‘landingbadge’) !== -1){
b.push(divs[i]);
}

}
for(var i=0;b[i];i++){
var badgecfg = convertClassData(b[i].className);
var link = b[i].getElementsByTagName(‘a’)[0];
if(link){
var linkdata = link.getAttribute(‘href’).split(‘brand=’)[1];
badgecfg.brand = linkdata;
}

var div = buildBadge(badgecfg);
if(div){
b[i].parentNode.replaceChild(div,b[i]);
}

}
function buildBadge(badgecfg){
if(badgecfg){
var div = document.createElement(‘div’);
div.innerHTML = ‘

Awesome badge!

‘;
if(badgecfg.brand){
div.appendChild(document.createTextNode(badgecfg.brand));
}

var col,width;
switch(badgecfg.size){
case ‘small’:width = 100;break;
case ‘large’:width = 400;break;
default:width = 200;break;
}

switch(badgecfg.skin){
case ‘blue’:col = ‘#ccf’;break;
case ‘green’: col = ‘#cfc’;break;
default:col = ‘#ccc’;break;
}

div.style.background = col;
div.style.width = width + ‘px’;
return div;
}

}
function convertClassData©{
var chunks = c.split(’ ‘);
var badgecfg = {};
for(var i=0,j=chunks.length;i var vp = chunks[j].split(‘-’);
if(vp[1]){
badgecfg[vp[0]] = vp[1];
}

}
return badgecfg;
}

})();

Hey, you use classes, why not provide a skin file?

Seeing that the last option actually uses classes, why not leave the styling to CSS and offer some skinning files the implementer can change? That way your badge script would be very small indeed:


(pebadge = function(){
var divs = document.getElementsByTagName(‘div’);
var b = [];
for(var i=0;divs[i];i++){
if(divs[i].className.indexOf(‘skinnedbadge’) !== -1){
b.push(divs[i]);
}

}
for(var i=0;b[i];i++){
var link = b[i].getElementsByTagName(‘a’)[0];
if(link){
var div = document.createElement(‘div’);
var linkdata = link.getAttribute(‘href’).split(‘brand=’)[1];
div.appendChild(document.createTextNode(linkdata));
div.innerHTML = ‘

Awesome badge!

‘;
b[i].parentNode.replaceChild(div,b[i]);
}

}
})();

You can extend that to load and apply CSS files on demand, but it’ll make more sense to keep them in one file, once again to cut down on HTTP overhead but also to use the cascade to produce small CSS files.

Comments? You can go and try out all the examples here

Retrieving del.icio.us tags for the current URL with JavaScript

Monday, February 11th, 2008

If you scroll down the older entries of this blog you’ll see that there is a new feature, namely a box that shows reader tags and a link to del.icio.us:

Screenshot of a list of tags with a link to del.icio.us

This is not a WordPress plugin (although it would be easy to make and i’d be amazed if it hadn’t been done) but pure JavaScript. You can also download the script that does this and use the following to embed it in any page you’d like to know the delicious data for:




There is not much magic going on here, I basically souped up the example on the del.icio.us site,minified and embedded Paul Johnson’s implementation of MD5 in JavaScript and created the necessary HTML.

The HTML structure inside the DIV will be a definition list with tags as dd’s and the text as the dt and a paragraph with a link. You can style it by using the #deliciousinfo ID.

I like the outcome and I am always amazed what good tags readers of my stuff come up with. If you want to know, get the src commented version and check the information in there.

Shall I create a WordPress plugin for this?

Edit: if you wondered what the difference to the tagometer is, there isn’t much, I just forgot about it….