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

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

  const mergedIntervals: number[][] = [intervals[0]];
  for (let i = 1; i < intervals.length; ++i) {
    const currentInterval = intervals[i];
    const lastMergedInterval = mergedIntervals[mergedIntervals.length - 1];

    if (currentInterval[0] > lastMergedInterval[1]) {
      mergedIntervals.push(currentInterval);
    } else {
      // Merge overlapping intervals
      lastMergedInterval[1] = Math.max(lastMergedInterval[1], currentInterval[1]);
    }
  }

  return mergedIntervals;
}
```