async-map.js

function after(times, callback) {
	return function() {
		times--;
		if(times === 0) {
			callback();
		}
	}
}

function asyncmap(list, op, cb) {
	var results = []
	var error = null;
	var done = after(list.length, function() {
		cb(error, results);
	});	

	list.forEach(function(item, i) {
		op(item, function(err, result) {
			if(err && !error) {
				error = err;
				cb(err);
			} else {
				results[i] = result;
				done();
			}			
		});
	});
}