You are reading someone else JavaScript code and you find this:
var checkshit = function(a, x) {
var ret, _i, _len;
if (x == null) x = 'checked';
var ret = true;
for (_i = 0, _len = a.length; _i < _len; _i++) {
if ((x === 'checked' && !a[_i].checked) || (x === 'unchecked' && a[_i].checked)) {
ret = false;
}