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
    Responsive Images: The Ultimate Guide

    Chances are that any Web designers using our Ghostlab browser testing app, which allows seamless testing across all devices simultaneously, will have worked with responsive design in some shape or form. And as today's websites and devices become ever more varied, a plethora of responsive images...

  • By
    Convert XML to JSON with JavaScript

    If you follow me on Twitter, you know that I've been working on a super top secret mobile application using Appcelerator Titanium.  The experience has been great:  using JavaScript to create easy to write, easy to test, native mobile apps has been fun.  My...

Incredible Demos

  • By
    Rotate Elements with CSS Transformations

    I've gone on a million rants about the lack of progress with CSS and how I'm happy that both JavaScript and browser-specific CSS have tried to push web design forward. One of those browser-specific CSS properties we love is CSS transformations. CSS transformations...

  • By
    Build a Toggling Announcement Slider Using MooTools 1.2

    A few of my customer have asked for me to create a subtle but dynamic (...I know...) way for them to advertise different specials on their website. Not something that would display on every page, but periodically or only the homepage. Using a trick...

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!