Callbacks & Callback Hell

What pattern does this implementation demonstrate?

function sequence(tasks, finalCallback) {
  const results = [];
  function next(index) {
    if (index === tasks.length) {
      return finalCallback(null, results);
    }
    tasks[index]((err, result) => {
      if (err) return finalCallback(err);
      results[index] = result;
      next(index + 1);
    });
  }
  next(0);
}

Parallel execution
Sequential execution
This code implements sequential execution of asynchronous tasks using callbacks. Important aspects: 1) Tasks execute one after another in order, 2) Results are collected in sequence, 3) Uses recursion to manage the sequence, 4) Handles errors by stopping the sequence, 5) Maintains order of execution and results, 6) Useful when tasks depend on previous results or must execute in specific order.
Random execution
Concurrent execution

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