anchor-headings.js

Array.prototype.splice.call(document.querySelectorAll("h2,h3,h4,h5,h6"), 0).
    map(function (el, n) {
        var txt, id;

        id = el.getAttribute("id");
        txt = el.innerText;

        if (!id) {
            el.setAttribute("id", encodeURIComponent(txt));
        }

        return el;
    }).
    forEach(function (el) {
        var a = document.createElement("a");
        a.setAttribute("href", "#" + el.getAttribute("id"));
        a.appendChild(el.firstChild);
        el.appendChild(a);
    });
    

navlistgen.js

var navlist = Array.prototype.splice.call(document.querySelectorAll("h2,h3,h4,h5,h6"), 0).
    map(function (el, n) {
        var txt, id;

        id = el.getAttribute("id");
        txt = el.innerText;

        if (!id) {
            el.setAttribute("id", encodeURIComponent(txt));
        }

        return el;
    }).
    map(function (el) {
        var a = document.createElement("a");
        a.setAttribute("href", "#" + el.getAttribute("id"));
        a.appendChild(document.createTextNode(el.innerText));
        return a;
    }).
    map(function (a) {
        var li = document.createElement("li");
        li.appendChild(a);
        return li;
    }).
    reduce(function (ul, li) {
        ul.appendChild(li);
        return ul;
    }, document.createElement("ul"));