How to return only the Date from a SQL Server DateTime datatype

How do i make a string from an array, saving all the square brackets

I have an array:

myArr = [[1, 2, 3], [4, 5, 6]]

And i want to make it a string like this:

newArr = "[[1, 2, 3], [4, 5, 6]]"

I have tried:

myArr.toString()
String(myArr)
myArr = `${myArr}`

But the result is allways

'1,2,3,4,5,6'