Javascript Incompatibilities/Inconsistencies [closed]

Answer 1

For the Date object:

alert( (new Date()).getYear();

Firefox returns 109

Internet Explorer returns 2009

Answer 2

With HTML markup like

<div id="foo">
    <a href="#">Link 1</a>
</div>

If you obtain a reference to the outer div, it will have one child node in some browsers, and three child nodes in others, depending on how whitespace is treated. Some will have text nodes with the newline and whitespace as children of div#foo before and after the link element.

Answer 3

alert(document instanceof Document)

in Firefox: true!

in Internet Explorer: exception: Document is undefined

Answer 4

DOM API inconsitencies aside (which is what libraries solve), there aren't many.

But some JS engines have implemented more features, like [].map(), [].filter() etc, let statement or E4X. When I switch between Mozilla-targeted development (Firefox extensions, server-side with Jaxer) and general browser tageted development (websites) I need to remember what's available in every browser, and what isn't. So it's all about what is implemented, not how it is done.