Error propagation

f1(function(err) {
    console.log(err);
});

function f1(callback) {
    // throw new Error("You can catch me.");

    f2(function(err) {
        if (err) return callback(err);
        
        f3(function(err) {
            if (err) return callback(err);
            
            return callback(null);
        })
    })
}

function f2(callback) {
    // return callback(new Error("I'll propagate through the callback."))

    return callback(null);
}

function f3(callback) {
    throw new Error("I'm the gingerbread man and I'll crash your program.");
}