```ts
export function mergeIntervals(intervals: number[][]): number[][] {
  const sortedIntervals = intervals.sort((a, b) => a[0] - b[0]);
  const mergedIntervals: number[][] = [sortedIntervals[0]];

  for (let i = 1; i < sortedIntervals.length; i++) {
   	const currentInterval = sortedIntervals[i];
    const lastMerged = mergedIntervals[mergedIntervals.length - 1];

    if (currentInterval[0] <= lastMerged[1]) { // Overlapping intervals
      lastMerged[1] = Math.max(lastMerged[1], currentInterval[1]);
    } else {
      mergedIntervals.push(currentInterval); // Non-overlapping interval
    }
  }

  return mergedIntervals;
}
```