Javascript - Adding arrays

Question

I understand sum is [1, 23, 4], but why length is 6?

var nums1 = [1,2];
var nums2 = [3,4];
var set = nums1 + nums2;
console.log(set.length);
console.log(set);

Answer 1

the sum of array is a string data type.

[1,2]+[3,4]==="1,23,4"
//true

I hope this will help you to understand.

Answer 2

the length is 6 because it sees the commas as part of the string.