function display(array, cb) {
var index = -1, length = array.length, $elem = $('.box');
while (++index < length) {
(function(html){
setTimeout(function() {
$elem.html(html)
}, index * 1000);
})(array[index]);
}
setTimeout(cb, index * 1000);
}

display([
'a',
'b',
'c'
], function() {
console.log('done');
})