this problem covers the basic understanding of how we can merge the two arrays if there values overlaps

mergeArray.js

// Input: [[1,3],[2,6],[8,10],[15,18]];
// Output: [[1,6],[8,10],[15,18]];
// Explaination: Since intervals [1,3] and [2, 6] overlaps, merge them into [1, 6].

var arr = [[1,3],[2,6],[8,10],[15,18]];
var newArr = [];
var index = 0;
while (index <= arr.length-1) {
	var currentVal = arr[index];
  var nextVal = arr[index+1] || 0;
	if(nextVal[0] <= currentVal[1]){
		newArr.push([currentVal[0], nextVal[1]]);
		index += 2;
	} else {
		newArr.push(currentVal);
		index += 1;
	}
	
}