Why am i getting diffrent outputs

now adding " " to the code the output changes

Its same output but in first case array is getting printed i.e.
[1, 2, 3, 4] and so on.
But when you add " " it converts this array to string so output is:
1,2,3,4 and so on

why does adding " " converts the array into a string

Because we are adding string type to array so whole thing will be converted to string