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

  intervals.sort(([start1, end1], [start2, end2]) => start1 - start2);

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

  for (let i = 1; i < intervals.length; i++) {
    const interval = intervals[i];
    if (interval[0] <= currentInterval[end1]) {
      // Merge the intervals
      currentInterval[1] = Math.max(currentInterval[1], interval[1]);
    } else {
      // Add the current interval to the result
      result.push(currentInterval);
      currentInterval = interval;
    }
  }

  // Add the last interval if it hasn't been added yet
  result.push(currentInterval);

  return result;
}
```