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

  intervals.sort((a, b) => a[0] - b[0]);

  const result: number[][] = [intervals[0]];

  for (let i = 1; i < intervals.length; i++) {
    const lastInterval = result[result.length - 1];

    if (lastInterval[1] >= intervals[i][0]) {
      lastInterval[1] = Math.max(lastInterval[1], intervals[i][1]);
    } else {
      result.push(intervals[i]);
    }
  }

  return result;
}
```