window.addEventListener("DOMContentLoaded", function() {
function scrollToElement(element, duration) {
var to = element.getBoundingClientRect().top;
var from = window.pageYOffset;
var start = performance.now();
requestAnimationFrame(function animate(time) {
var progress = (time - start) / duration;
1 <= progress && (progress = 1);
window.scrollTo(0, from + to* progress | 0);
1 > progress && requestAnimationFrame(animate)
})
}
var nav = document.querySelector(".nav"),
button = nav.querySelectorAll(".nav__link"),
block = document.querySelectorAll(".content .block");
nav.addEventListener("click", function(event) {
var target = event.target;
if (target = target.closest(".nav__link")) {
event.preventDefault();
var indx = [].indexOf.call(button, target);
if (indx !== -1) scrollToElement(block[indx], 800)
}
})
});