function setPageContent(elemID) {
    let elem = document.querySelector(elemID);
    let target = document.querySelector("#page-content");
    target.style.opacity=0;
    setTimeout(function () {
        target.innerHTML = elem.innerHTML;
        target.style.opacity = 1;
    }, 500);
}

function nextPage() {
    page = Math.min(page+1, pages.length-1);
    setPageContent(pages[page]);
}

function prevPage() {
    page = Math.max(page-1, 0);
    setPageContent(pages[page]);
}

function showLoader(opacity) {
    let elem = document.querySelector("#loading-page");
    elem.style.opacity = opacity ? 1 : 0;
    if (opacity) {
        elem.style.display = "flex";
    } else {
        setTimeout(function () {
            elem.style.display = "none";
        }, 500)
    }
}