Javascript is a fantastic language — in fact, it’s become the language that I do most of my programming in nowadays. It’s flexible, fast, and powerful. Unfortunately, though, it suffers from a few flaws, which, although not critical, can be frustrating. One of the potentially most confusing features is the with keyword, which promises a lot, but can really just make life difficult.

The with keyword might appear to be harmless enough: it allows you to avoid typing long references; instead of

ah.woom.ba.weh.lyric = 'In the jungle';

we can type

with (ah.woom.ba.weh) {
  lyric = 'In the jungle';
}

But what happens if we happen to have a global variable named lyric? In the example below, which lyric should be modified?

lyric = 'In the jungle';
with (ah.woom.ba.weh) {
  lyric = 'The mighty jungle';
}

The simplest way to deal with this issue is to use a variable:

var a = ah.woom.ba.weh;
a.lyric = 'The mighty jungle';

Now there is no ambiguity.

Based on a post by Douglas Crockford at the YUI Blog.

At work, I’ve recently been putting together a nice little calendar-like utility using Javascript. Basically, it has to generate a table consisting of cells which may span multiple rows. Surely the solution is simple enough: just set the rowspan on each td as we create it. Unfortunately, that doesn’t work, at least not in Firefox.

It appears that in Firefox, if you create a td and set its rowspan to some value when there are no rows for it to expand into, the attribute will be completely ignored, even if you add rows afterwards! Needless to say, this is very annoying. The solution? Build your table backwards.

The code I have now is something like this (note that I’m developing using the Mootools framework):

var tbl = new Element('table');
var trs = new Array();

for (var i = 0; i < 4; i++) {
  var tr = new Element('tr');
  tr.grab(new Element('td', {
    'html': 'Cell ' + i
  }));
  if (i % 2 == 0) {
    tr.grab(new Element('td', {
      'rowspan': 2,
      'html': 'Span ' + (i / 2)
    }));
  }
  trs.push(tr);
}

for (var i = trs.length - 1; i >= 0; i--) {
  tbl.grab(trs[i], 'top');
}

What does this code do? Well basically, we’re creating a table with ten rows and two columns; the cells in the right-hand column each occupy two rows. The result will be something like this:

I’ve started work on a new project at my job — a fairly complex AJAX application for the education sector. For this project, I’ve been allowed to essentially choose my own direction, and I’ve chosen to implement the clientside Javascript using the MooTools framework. I’ll say it right here: I’m absolutely loving it.

What I’m really enjoying about MooTools is the object-orientedness it brings to development. Although syntactically it’s a little bit weird at first, the ability to create, extend, and implement classes makes my development progress much more quickly, and in a more efficient way. Add to that the plethora of utilities (like the .each prototype for arrays) and shorthand functions (like $ to replace document.getElementById), and all of a sudden Javascript development becomes a bit more, well, flexible.

I’m not saying that you can’t accomplish cool things in Javascript outside of MooTools (or other frameworks, for that matter); my point is that I believe you can accomplish cool things in Javascript more quickly using a good framework, which should really come as no surprise. Perhaps the reason I’m so enjoying this type of development, to the point of blogging about it, is that up till now, I’ve been stuck working in a non-frameworked, very non-OO Javascript development paradigm.

I mentioned the curious syntax that accompanies MooTools.  To create a new class, for example, you would probably write something like this:

var myClass = new Class({
  Implements: Options,
  options: {
    optionA: 'monkey',
    optionB: 'pony'
  },
  initializer: function(options) {
    this.setOptions(options);
    this.doSomeStuff();
  },
  doSomeStuff: function() {
    alert(this.options.optionA + ' eats ' + this.options.optionsB);
  }
});

And then you would initialise it like this:

var myInstance = new myClass({
  optionA: 'Big Pony'
});

Although it looks a bit weird, it’s actually not too bad. There are really only two problems I have with it:

1. Remembering to put commas in all the right spots.
2. Geany, my preferred IDE (cf. Geany IDE: Tango dark colour scheme) can’t pick up classes and members properly (actually, at all) in this style.

Other than that, though, I’m really enjoying it.

In this post, I’ll outline some of the web developer tools available in the major browsers: Firefox, Internet Explorer, Opera and Safari. This is a wholly subjective post, based on my experience as one of two developers on a very large AJAX application at Saron Education.

Firefox

Firefox has arguably got the best web development tools available, all of which can be downloaded from the Firefox Addons site. The two which I find most useful are the Web Developer Toolbar, by Chris Pederick, and the often-copied Firebug (official website), which itself sports a variety of addons.

Web Developer Toolbar

The web developer toolbar is useful for quickly enabling and disabling features of your site, checking CSS, emulating mobile browser rendering, and controlling Firefox more precisely. Personally, I find its most useful features are the ability to:

• Disable the browser cache entirely, which removes the need for Control-Refresh or cache-clearing;
• Outline deprecated elements, or any particular set of elements in a variety of fashions, which is very useful for updating old sites;
• Extract colour information from the current website; and
• View the cookie information for the current site.

Download the Web Developer Toolbar

Firebug

I sometimes wonder how I ever managed to develop web applications without Firebug. Firebug allows you to alter CSS styles on the fly, edit the HTML contents of the page on the fly, visually watch the DOM being changed by your scripts, debug your scripts, type and run JavaScript straight from the browser, visualise network activity, inspect XMLHttpRequests, and much much more besides. Firebug is, in my experience, the most mature, stable, and efficient of all the tools in this survey.

The features of Firebug which I find most useful are:

• The ability to ‘inspect’ the DOM visually (by clicking on elements within the page), then alter their attributes, styles, and even their content dynamically;
• The ability to watch the effects of DOM alterations by running scripts;
• The console, with which you can craft and run JavaScript which is run as though it were part of the page itself;
• The network monitor, which allows you to view all the POSTs and GETs your XMLHttpRequests create.

Download Firebug

Internet Explorer

Until IE 8, the tools available to developers in IE were woeful at best. Fortunately, however, Microsoft has got their act together, and mimicked Firebug for version 8. The features made available in this tool include

• The ability to interrogate the DOM to view style information about elements (changing attributes and styles hardly ever seems to work in the latest Beta, so viewing them is all you can really achieve);
• A console, with which you can craft and run Javascript as though it were embedded in the page;
• Javascript debugging.

Unfortunately, these tools are still very much in beta, and are very buggy. As I mentioned, altering element attributes and styles hardly has any effect. Also, the CSS inspection system is poorly laid out and often just plain wrong. The console is well-implemented. The entire system is definitely a step in the right direction, but it suffers from bugs and lack of innovation. Also, it seems to slow down and destabilise the entire browser.

Internet Explorer 8′s developer tools are built in; access them with the F12 key.

Opera

Opera’s developer tools, codenamed ‘Dragonfly’, sit between Firebug and IE in terms of functionality and facility. The DOM inspection and manipulation tools work really well (as well as Firebug), and are more immediately configurable, thanks to a variety of toolbar buttons. Dragonfly doesn’t have a console; rather, it uses a ‘command line’ interface. The difference is that where the console in Firebug and IE has seperate areas for input and output (what you type and what it does), the command line mixes these two together, much like a Unix shell or DOS. Personally, I prefer the console paradigm, but it’s much of a muchness.

Opera’s Dragonfly is built in; access it by going to Tools -> Advanced -> Developer tools.

Safari

As with most Apple products, the developer tools in Safari are very pretty. There is a console akin to that in Firebug and IE, and you can inspect and manipulate the DOM. Unfortunately, however, the tools are quite buggy, and often fall down. Whilst the tools are very pretty, they don’t seem to be as stable even as IE 8′s.

Safari’s web developer tools are built in; access them enabling the develop menu from the Advanced tab of the config, then choosing the appropriate menu item from the Develop menu.

Conclusions

Whilst Firebug is still by far the best tool available for web developers, the widespread development of tools by browser developers means that cross-browser debugging and development is becoming ever easier. Hopefully the tools will foster competition, so that feature sets and stability improve in all the tools.