Creating an element in an element with Jquery

I'm trying to create an element with an element inside of it in JQuery, but I'm not getting anything when I try and output it.

This is the HTML equivalent of what I'm looking for:

HTML:

<div class="btn-icn">
<button class="btn"><span class="glyphicon glyphicon-comment"></span>
</button></div>

Jquery:

a = $(button).attr({
class: "btn";
id:"btn";
}.append($(icon).attr({
class:"glyphicon glyphicon-comment";
id="comment";
}));
)

alert(a);

Thanks!