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

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

  const merged: number[][] = [];
  let currentInterval = intervals[0];

  for (const interval of intervals.slice(1)) {
    if (interval[0] > currentInterval[1]) {
      merged.push(currentInterval);
      currentInterval = interval;
    } else if (interval[1] > currentInterval[1]) {
      currentInterval = [currentInterval[0], interval[1]];
    }
  }

  merged.push(currentInterval);

  return merged;
}
```