Troubleshooting CSS Style Assignments within Dojo

By  on  

I was recently working on a Dojo project which used a series of JavaScript calculations to generate CSS style values. While calculating styles with JavaScript is quite common, especially when attempting to dynamically position HTML nodes, values aren't always cleansed the way that they should be. Safari and Firefox appear to ignore invalid style values but Internet Explorer tends to throw errors when a bad style or value is assigned to a node. After digging through tons of code to find a possible problem, I chose create a modified dojo.style snippet which would help me find problem styles.

The Dojo Toolkit JavaScript

The snippet is actually quite small and only adds to Dojo's native dojo.style method:

//save original method
var oldDojoStyle = dojo.style;
//create our own custom version
dojo.style = function() {
	//debug
	if(arguments.length == 3) {
		//make arguments readable
		var node = arguments[0], attribute = arguments[1], value = arguments[2];
		//decide to warn or log
		var method = (value == undefined || value == null || value == '' || value.toString().indexOf('NaN') != -1 ? 'warn' : 'log' );
		//execute!
		console[method]('Setting "' + attribute + '" to: "' + value + '" on ',node,';; arguments: ',arguments);
	}
	//call origonal method
	oldDojoStyle.apply(dojo, arguments);
}

The first step is saving the original dojo.style method so it may be called from the new dojo.style method we create. Then we create a new dojo.style method declaration which contains a series of console.log/warn logic to output invalid CSS values, like null, undefined, and NaN. When a potentially bad value is provided, a console.warn warning is sent to the console.

A sample bit of output would be:

Dojo Style

You could use an alert() call to make the error more noticeable but I prefer using console because I can pass the actual arguments object to the console to get more information about the issue.

And there you have it. I know this is super simple but it can also save you lots of time in finding what style assignment is causing you problems!

Recent Features

  • By
    CSS 3D Folding Animation

    Google Plus provides loads of inspiration for front-end developers, especially when it comes to the CSS and JavaScript wonders they create. Last year I duplicated their incredible PhotoStack effect with both MooTools and pure CSS; this time I'm going to duplicate...

  • By
    Facebook Open Graph META Tags

    It's no secret that Facebook has become a major traffic driver for all types of websites.  Nowadays even large corporations steer consumers toward their Facebook pages instead of the corporate websites directly.  And of course there are Facebook "Like" and "Recommend" widgets on every website.  One...

Incredible Demos

  • By
    Dynamically Load Stylesheets Using MooTools 1.2

    Theming has become a big part of the Web 2.0 revolution. Luckily, so too has a higher regard for semantics and CSS standards. If you build your pages using good XHTML code, changing a CSS file can make your website look completely different.

  • By
    Implement jQuery’s hover() Method in MooTools

    jQuery offers a quick event shortcut method called hover that accepts two functions that represent mouseover and mouseout actions. Here's how to implement that for MooTools Elements. The MooTools JavaScript We implement hover() which accepts to functions; one will be called on mouseenter and the other...

Discussion

  1. I did something similar once, but rather than monkey patching dojo.style, I just connected to it – something like this: http://jsfiddle.net/brianarn/k7aZG/

    That way, I don’t have to save a reference to the original method. Arguably, it’s doing the same thing here (since connect is kind of like a fancy monkey patcher of sorts), but it just feels a bit cleaner to me.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!