How to make th

q.js

var id = 1;

function drop(name, callback) {
    setTimeout(function(){callback(name)}, 3000);
}

function insert(dataArr, callback) {
    dataArr.forEach(function(item) {
	item._id = id++;
    });
    setTimeout(function(){callback(dataArr)}, 1000);
}

// I want to drop all tables first

['aaa','bbb','ccc'].forEach(function(name){
    drop(name, function(name){
	console.log(name + ' is dropped');
    });
});


// !!! how to make sure all tables are dropped before inserting?
console.log('all tables are dropped');

// I want to insert some data

// !!! how to reduce the callbacks

// insert users
insert([{name:'a'},{name:'b'}], function(users) {
    console.log('inserted users');
    var user1 = users[0], user2 = users[1];

    // insert categories
    insert([{name:'c', userId:user1._id},{name:'d',userId:user2._id}], function(categories) {
	console.log('inserted categories');
	var category1 = categories[0], category1 = categories[1];

	// insert questions
	insert([{name:'e',userId:user1._id,categoryId:category1._id}], function(questions) {
	    console.log('inserted questions');

	    var question1 = questions[0];

	    // insert answers
	    insert([{name:'g', userId:user1._id, questionId: question1._id}], function(answers){
		console.log('inserted answers');

		var answer1 = answers[0];

		// insert comments
		insert([{name:'i', userId:user1._id, answerId:answer1._id}], function(comments){
		    console.log('inserted comments');

		    var comment1 = comments[0];
		    // insert replies
		    insert([{name:'k',commentId:comment1._id}], function(replies){
			console.log('inserted replies');

			// do you want more :)
			console.log('finished');
		    });
		});
	    });
	});
    });
});