Why is [1,2] + [3,4] = “1,23,4” in JavaScript?

Question

I wanted to add the elements of an array into another, so I tried this:

[1,2] + [3,4]

It responded with:

"1,23,4"

What is going on?

Answer 1

It is because, + operator assumes that the operands are string, if they are not numbers. So, it first converts them to string and concats to give the final result , if its not a number. Also, it does not support arrays.