Merge Intervals Medium

Given an array of intervals [start, end], merge all overlapping intervals and return the non-overlapping intervals covering the same ranges, sorted by start. Intervals that touch at an endpoint overlap.

Examples

• [[1,3],[2,6],[8,10],[15,18]] -> [[1,6],[8,10],[15,18]]
• [[1,4],[4,5]] -> [[1,5]]

Define a function named merge in JavaScript.