map & reduce with Promise

function workMyCollection(arr) {
    return q.all(arr.map(function(item) {
        return doSomethingAsync(item);
    }));    
}

function workMyCollection(arr) {
    return arr.reduce(function(promise, item) {
        return promise.then(function(result) {
            return doSomethingAsyncWithResult(item, result);
        });        
    }, q());
}