CODE EXAMPLE FOR JAVASCRIPT

animated scroll to anchor without jquery

const requestAnimationFrame = window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    window.msRequestAnimationFrame;

function scrollTo(to) {
    const start = window.scrollY || window.pageYOffset
    const time = Date.now()
    const duration = Math.abs(start - to) / 3;

    (function step() {
        var dx = Math.min(1, (Date.now() - time) / duration)
        var pos = start + (to - start) * easeOutQuart(dx)

        window.scrollTo(0, pos)

        if (dx < 1) {
            requestAnimationFrame(step)
        }
    })()
}