scrolling.js

<script>
function Scroll(delay) {
    this.initialY = scrollY;
    this.callbacks = {
        start  : null,
        scroll : null,
        end    : null,
    };
    this.timeout = {
        delay  : delay || 150,
        handle : null,
    };
    this.handler = Scroll.handler.bind(this);
    window.addEventListener("scroll", this.handler);
}

Scroll.handler = function (e) {
    if (this.initialY == 0) {
        if (this.timeout.handle == null) {
            if (this.callbacks.start) {
                this.callbacks.start.call(this, e);
            }
        }
        if (this.timeout.handle !== null) {
            clearTimeout(this.timeout.handle);
        }
        if (this.callbacks.scroll) {
            this.callbacks.scroll.call(this, e);
        }
        var self = this;
        this.timeout.handle = setTimeout(function () {
            self.timeout.handle = null;
            if (self.callbacks.end) {
                self.callbacks.end.call(self, e);
            }
        }, this.timeout.delay);
    } else {
        this.initialY = 0;
    }
};

Scroll.prototype.addEventListener = function (event, callback) {
    if (Object.keys(this.callbacks).includes(event)) {
        this.callbacks[event] = callback;
    } else {
        console.warn("Invalid scroll event: " + event);
    }
};

window.addEventListener('DOMContentLoaded',() => {
    let tocLinks = document.getElementsByClassName('toc-link');
    
    for(let i = 0; i < tocLinks.length; i++) {
        tocLinks[i].addEventListener('click', () => {
            for(let i = 0; i < tocLinks.length; i++) {
                tocLinks[i].classList.add('toc-unstyled')
            }
        })
    }
    
    var sl = new Scroll(400);
    
    sl.addEventListener("end", function () {
        for(let i = 0; i < tocLinks.length; i++) {
            tocLinks[i].classList.remove('toc-unstyled')
        }
    });
});
</script>