how to change an element type using jquery

Here’s one way you could do it with jQuery:

var attrs = { };

$.each($("b")[0].attributes, function(idx, attr) {
    attrs[attr.nodeName] = attr.nodeValue;
});


$("b").replaceWith(function () {
    return $("<h1 />", attrs).append($(this).contents());
});

Example: http://jsfiddle.net/yapHk/

Update, here’s a plugin:

(function($) {
    $.fn.changeElementType = function(newType) {
        var attrs = {};

        $.each(this[0].attributes, function(idx, attr) {
            attrs[attr.nodeName] = attr.nodeValue;
        });

        this.replaceWith(function() {
            return $("<" + newType + "/>", attrs).append($(this).contents());
        });
    };
})(jQuery);

Example: http://jsfiddle.net/mmNNJ/