The lazy programmer at work: _eoo and your Javascript Objects

Whenever you create an object in JS, you do somehting like this (at least that’s how I do it):

// A Javascript Object
var MyJsObject = {
	param1: true,
	param2: false,
	func1 : function() {
		// my code here
	}
}

Whenever you expand that object, one would add a new function/param to the object, separated by a comma:

// Expanding the Object
var MyJsObject = {
	param1: true,
	param2: false,
	param3: "Yes we can",
	func1 : function() {
		// my code here
	},
	func2 : function() {
		// my code here
	}
}

Now, I myself have noticed that sometimes I forget to add a comma, like so:

// This will fail
var MyJsObject = {
	param1: true,
	param2: false,
	param3: "Yes we can"
	func1 : function() {
		// my code here
	},
	func2 : function() {
		// my code here
	}
}

The above of course won’t go undetected, as it will produce an error. Using Firebug you’ll get this lovely error, pointing you immediately towards the errorous file:

Another mistake one can make is to have an extra comma after your very last function. This – for example – can happen when you delete a function from the object:

// This will fail, will it?
var MyJsObject = {
	param1: true,
	param2: false,
	param3: "Yes we can",
	func1 : function() {
		// my code here
	},
}

The problem with the above is that it won’t give an error in Firefox (my weapon of choice), allowing to code along without even knowing I’ve left a lost comma at the very end of my JS file!

The real problem of the problem above is that it actually will give an error in – yeah, you’ve guessed it – Internet Explorer.

As many webdevelopers I test sites in IE not that often: I first get my stuff straight in Firefox, and then test IE and start fixing the errors.

Now, there’s a problem with “the problem of the problem”: IE gives an error, but – again, you’ve guessed it right – it totally isn’t descriptive; You get something like: “Line: 10; Char: 1; Error: Expected identifier, string or number; Code: 0; File: yourpage.html”

The error given is worthless as neither the correct file nor the correct line-number is mentioned in the error! Finding the file that’s causing the error can take quite some time if you have lots of JS files.

In order to never ever mistakenly produce such an error I use this little trick: the very last datamember/property/whatever-you-like-to-call-it of every Object I write is a dummy parameter _eoo, which is short for End Of Object. This _eoo always is the last datamember of the Object, as seen below:

// "Bramus! The lazy programmer" at work
var MyJsObject = {
	param1: true,
	param2: false,
	param3: "Yes we can",
	func1 : function() {
		// my code here
	},
	_eoo: true
}

Using the _eoo trick, one can never – mistakenly – have a lost comma at the end and one must always add a comma when adding new functions/datamembers (which you do before the _eoo param). This reduces mistakes, as there’s no doubt anymore 🙂

Turns out that this little trick is that good, that my former colleagues at Netlash and Netlog are using this trick too nowadays 🙂