.js

function process(chunks, index) {
    var chunk = chunks[index];
    if (_.isUndefined(chunk)) {
        return;
    };  
    console.log('doing expensive work ' + _.last(chunk));
    _.defer(_.partial(process, chunks, ++index));
}

var collection = _.range(10000),
    chunks = _.chunk(collection, 50);

process(chunks, 0);
// → 
// doing expensive work 49
// doing expensive work 99
// doing expensive work 149