headroom-settings.js

// must come after wp_footer();
var elem = document.querySelector("#masthead");
var headroom = new Headroom(elem, {
    "offset": 100,
    "tolerance": 8,
    "classes": {
        "initial": "headroom",
        "pinned": "headroom--is-pinned",
        "unpinned": "headroom--is-hidden"
    }
});
headroom.init();