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

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

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

    if (current[0] > previous[1]) {
      merged.push(current);
    } else {
      // Adjust the end of the previous interval to cover the entire range
      previous[1] = Math.max(previous[1], current[1]);
    }
  }

  return merged;
}
```