var h2 = document.getElementsByTagName("h2");
for(var i=0;i<h2.length;i++) {
    h2[i].onclick = function() {
        var uls = this.nextElementSibling;
        console.log(uls)
        if(uls.style.display == 'block') {
            uls.style.display = 'none';
        } else {
            uls.style.display = 'block'
        }
    }
}