```typescript
export function mergeIntervals(intervals: number[][]): number[][] {
  if (!intervals || intervals.length === 0) return [];

  intervals.sort(([aStart, aEnd], [bStart, bEnd]) => aStart - bStart);

  const result: number[][] = [];
  let currentInterval: number[] | null = null;

  for (const interval of intervals) {
    if (!currentInterval || interval[0] > currentInterval[1]) {
      currentInterval = interval;
      result.push(currentInterval);
    } else {
      currentInterval[1] = Math.max(currentInterval[1], interval[1]);
    }
  }

  return result;
}
```