Determining Object Type with MooTools’ typeOf

By  on  

One thing about JavaScript I dislike is the vagueness of what the typeof operator returns. Pass typeof an array? You get "object" back (which it is, but a more concise answer would be helpful). Pass typeof a Date object? You get "object" again. What if there was a better way of determining an object's descriptive type? That's where the typeOf function within MooTools Core comes into play.

typeOf Source and Usage

The typeOf function is actually quite short:

var typeOf = this.typeOf = function(item){
	if (item == null) return 'null';
	if (item.$family) return item.$family();

	if (item.nodeName){
		if (item.nodeType == 1) return 'element';
		if (item.nodeType == 3) return (/\S/).test(item.nodeValue) ? 'textnode' : 'whitespace';
	} else if (typeof item.length == 'number'){
		if (item.callee) return 'arguments';
		if ('item' in item) return 'collection';
	}

	return typeof item;
};

typeOf checks for specific properties on the object in question to determine its descriptive type. Simple, right? Note the $family() check within typeOf; each Type (Array, Function, Date, etc.) instance is given a $family method which returns its type. Let's try a few typeOf calls:

typeof document.body;  // returns "object"
typeOf(document.body);  // returns "element"

typeof new Date();  // returns "object"
typeOf(new Date());  // returns "date"

typeof [];  // returns "object"
typeOf([]);  // returns "array"

typeOf is an awesome utility function, right? Getting a more detailed object type than simply "object" can be hugely help in validating the object before using it. typeOf is just another awesome utility within the MooTools JavaScript framework.

Recent Features

  • By
    Introducing MooTools Templated

    One major problem with creating UI components with the MooTools JavaScript framework is that there isn't a great way of allowing customization of template and ease of node creation. As of today, there are two ways of creating: new Element Madness The first way to create UI-driven...

  • By
    Write Simple, Elegant and Maintainable Media Queries with Sass

    I spent a few months experimenting with different approaches for writing simple, elegant and maintainable media queries with Sass. Each solution had something that I really liked, but I couldn't find one that covered everything I needed to do, so I ventured into creating my...

Incredible Demos

  • By
    Create a CSS Flipping Animation

    CSS animations are a lot of fun; the beauty of them is that through many simple properties, you can create anything from an elegant fade in to a WTF-Pixar-would-be-proud effect. One CSS effect somewhere in between is the CSS flip effect, whereby there's...

  • By
    Create a Clearable TextBox with the Dojo Toolkit

    Usability is a key feature when creating user interfaces;  it's all in the details.  I was recently using my iPhone and it dawned on my how awesome the "x" icon is in its input elements.  No holding the delete key down.  No pressing it a...

Discussion

  1. I use the regular “typeOf” to determine if classes are present, but the MooTools typeOf is much better, and great for making sure variables are the correct type. I wish more plugin coders would return robust error messages with these kinds of checks.

  2. Nice one !!!!!!

  3. Lorenzo

    Anyone knows if Mootools’ typeOf is more reliable than standard typeof when I want to check if something is a function or not?

    var a = (function() { return true; });
    var b = { name: 'value' };
    // typeof(a) == typeOf(a) == 'function' is always TRUE?
    // typeof(b) == typeOf(b) != 'function' is always TRUE?
    
  4. Mootools supports another type check – the Type Object.
    Type.isNumber(var), Type.isObject() etc.

    This is nowhere in the docs (except once used in an example on the Array page). It is shorter and more semantic when you are checking for one type, don’t know why it is hidden.

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