javascript - Get clicked element onclick

var submenus = document.getElementsByClassName("submenu");
for (var i = 0; i < submenus.length; i++) {

    submenus[i].onclick = function() {
        toggle(submenus[i].nextSibling);
        return false;
    }
}

function toggle(el) {
    if (el.style.display == 'block') {
        el.style.display = 'none';
    } else {

        el.style.display = 'block';
    }
}

Causes error: TypeError: submenus[i] is undefined

I assume submenus[i] is not in the scope of the function. How do I get the element clicked so I can toggle it's next sibling?