var btnSearch = document.getElementsByClassName("button-search")[0];
var searchInput = document.getElementsByClassName("search-input")[0];

btnSearch.addEventListener("click", function (event) {
    event.preventDefault();
    searchInput.classList.toggle("active");
    this.disabled = true;
    searchInput.focus();
});

searchInput.addEventListener("blur", function (event) {
    this.classList.toggle("active");
    btnSearch.disabled = false;
});