Pure Vanilla JavaScript Smooth Scroll to Element on <a> anchor tag click #id

It took me half an hour and countless of stackoverflow pages to find a perfect solution for a smooth scroll for <a> anchor links.

So I'm adding here it as a snippet for future googlers.

document
    .querySelectorAll('.nav__item a[href^="#"]')
    .forEach(trigger => {
        trigger.onclick = function(e) {
            e.preventDefault();
            let hash = this.getAttribute('href');
            let target = document.querySelector(hash);
            let headerOffset = 100;
            let elementPosition = target.offsetTop;
            let offsetPosition = elementPosition - headerOffset;

            window.scrollTo({
                top: offsetPosition,
                behavior: "smooth"
            });
        };
    });

Note

Please note there is also a new CSS property available to do the same trick, however you won't be able to offset it properly. This will cause issue when you are using a fixed navbar. In that case, JS Solution will be better.