JavaScript: Open external links and specific file types in a new tab/window

gistfile1.js

$(document).ready(function() {
    /*-------------------------------------------------------------------
    | Force external links and specific files to open in a new window/tab
    *-------------------------------------------------------------------*/
    var externalProtocolRegex = /^https?:\/\//i;
    var externalRegex = (window.location.protocol + '//' + window.location.hostname).replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
    externalRegex = new RegExp('^(\/\/|' + externalRegex + ')');
    var fileRegex = /\.pdf$/;

    $('a[href!=""]').not('[target=_blank]').click(function(event) {
        var href = $(event.target).closest('a').attr('href');

        if (
            href &&
            (
                // Is it a protocol-relative URL?
                href.substring(0, 2) === '//' ||

                (
                    // Does it even start with something that would indicate an external URL?
                    // Checking for this eliminates relative and absolute path hrefs.
                    href.match(externalProtocolRegex) &&

                    // Does the provided domain match this site's?
                    !href.match(externalRegex)
                ) ||

                // Is it a specific file type?
                href.match(fileRegex)
            )
        ) {
            event.preventDefault();
            window.open(href, '_blank');
            return;
        }
    });
});