The couchapp framework comes with some excellent libraries for managing your Couch DBs. If you're developing a couchapp, the URIs to the needed JS will be along the lines:
<script src="/_utils/script/json2.js"></script>
<script src="/_utils/script/jquery.js"></script>
<script src="/_utils/script/jquery.couch.js"></script>
To create a new document, you can then just do:
<script type="text/javascript">
var hitData = {
"publication_id" : "1",
"content_id" : "66",
"section_id" : "22",
"created_at" : "",
"uri" : "/hit.html"
};
var $db = $.couch.db("memento");
$db.saveDoc(hitData);
</script>
