IE calls methods simply when accessed. This is not always an issue, but can be problematic. Below is a failing test case using XML. This issue warrants the need for other ways to check for the presence of methods.

ie_method_call.js

var xml = $.parseXML('<crazy><element>asdf</element><div>asdf</div></crazy>'),
    counter = 0;
console.log( xml, $(xml).find('*') );

$(xml).find('*').andSelf().each(function( i, elem ) {
    if ( elem.getElementsByTagName ) {
        counter++;
    }
});

console.log( counter );

http://jsperf.com/in-vs-typeof