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

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

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

  for (let i = 1; i < intervals.length; i++) {
    const currentStart = intervals[i][0];
    const currentEnd = intervals[i][1];
    const lastInterval = merged[merged.length - 1];

    if (currentStart <= lastInterval[1]) {
      // Merge the current interval with the last merged interval
      lastInterval[1] = Math.max(lastInterval[1], currentEnd);
    } else {
      // Add the current interval as a new merged interval
      merged.push(intervals[i]);
    }
  }

  return merged;
}
```