```ts
export function mergeIntervals(intervals: number[][]): number[][] {
  if (!Array.isArray(intervals) || intervals.length === 0) {
    throw new Error("Invalid input: Input must be a non-empty array of [start, end] pairs.");
  }

  // Sort intervals by their start values
  intervals.sort((a, b) => a[0] - b[0]);

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

  for (let i = 1; i < intervals.length; i++) {
    const nextInterval = intervals[i];
    
    if (currentInterval[1] >= nextInterval[0]) {
      // Merge the current interval with the next one
      currentInterval[1] = Math.max(currentInterval[1], nextInterval[1]);
    } else {
      // Add the current interval to mergedIntervals and update currentInterval
      mergedIntervals.push(currentInterval);
      currentInterval = nextInterval;
    }
  }

  // Add the last merged interval
  mergedIntervals.push(currentInterval);

  return mergedIntervals;
}
```