1let intervals = [
2  [1, 3],
3  [2, 6],
4  [8, 10],
5  [15, 18],
6];
7
8function mergeIntervals(intervals) {
9    if (intervals.length <= 1) {
10        return intervals;
11      }
12      intervals.sort((a, b) => a[0] - b[0]);
13
14      let merged = [];
15      let start = intervals[0][0];
16      let end = intervals[0][1];
17      for (let i = 1; i < intervals.length; i++) {
18        if (intervals[i][0] <= end) {
19            end = Math.max(end, intervals[i][1]);
20          }else { merged.push([start, end]);
21            start = intervals[i][0];
22            end = intervals[i][1];
23          }
24      }
25      merged.push([start, end]);
26      return merged;
27}
28
29console.log(mergeIntervals(intervals));
30