Detecting HTML <a> click-to-call support in Javascript

There are two ways to have click-to-call links in HTML

<a href="wtai://wp/mc;+1800229933</a> WTAI style (Nokia, others)
<a href="tel:+1-800-275-2273">Call Apple Customer Support at 1-800-275-2273</a>. TEL style (Apple)

How one can

detect which format is supported by current user agent in Javascript?
Is it possible to do the detection without relying the user agent string

More info

Solution

Maximiliano Firtman has a great article on how to create click-to-call links for mobile browsers. He states that the tel: protocol is supported by almost every mobile device, including: Safari on iOS, Android Browser, webOS Browser, Symbian browser, Internet Explorer, Opera Mini and low-end devices browsers.

Because of the wide support of the tel: protocol, I would suggest just use the tel: protocol. To support Nokia I would check if the navigator.userAgent contains Nokia footprint. If so, replace tel: to wtai://wp/mc;

If you can use jQuery, the Javascript could look something like:

if (/(Series60|Nokia)/i.test(navigator.userAgent)){
  $("a[href^='tel:']").each(function(){
    this.href = this.href.replace("tel:", "wtai://wp/mc;");
  });
}