Returns the name of the element.
elementName = element.tagName
elementNameis a string containing the name of the current element.
In XML (and XML-based languages such as XHTML),
tagName preserves case. On HTML elements in DOM trees flagged as HTML documents,
tagName returns the element name in the uppercase form. The value of
tagName is the same as that of nodeName.
Given the following markup:
<span id="born">When I was born...</span>
and the following script
var span = document.getElementById("born"); alert(span.tagName);
In XHTML (or any other XML format), "span" would be alerted. In HTML, "SPAN" would be alerted instead.