I'm new to filtering dates with REST in SP but am trying to do something like below but am not sure how to get today's date in as a variable into the request. I don't think I'm too far off so any help is greatly appreciated.
var today = new Date();
$.ajax({
url: "/_api/web/lists/GetByTitle('DateItems')/items?$orderby=SortOrder asc&$filter=StartDate le datetime'" + today + "' and EndDate ge datetime'" + today + "'",
...
});