DOM class property HTMLElement className when an element does not have a set of class names

Question

When you have an HTML element without a set of class names, what is the value of the property of the HTMLElement class? My first thought was that it is undefined, but I found that in FF it is just an empty string. My question is: can I rely on this behavior in all current and future browsers? Is this part of any specification or is it just another browser trick to avoid errors in poorly written code?

Answer 1

By default there will always be an empty string ( a DOMStringspecially ), and yes, you can rely on it without being null/ undefined.

The definition is really important here getAttribute():

Return Value DOMString
A value Attras a string or an empty string if this attribute does not have a specified or default value.

... it's really just an attribute that you throw back, so in both cases it is the same behavior, the interface just defines these attributes.

Answer 2

interface HTMLElement : Element {
           attribute  DOMString            id;
           attribute  DOMString            title;
           attribute  DOMString            lang;
           attribute  DOMString            dir;
           attribute  DOMString            className;
};

- http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001/level-one-html.html

Also see the definition of DOMString .

So it should be safe.