What is .map() doing in this situation?

Question

Using the Chrome Console, this is my input and output:

[0].map(Array);

[[0, 0, [0]]]; // output

What is happening here?

ED

Answer 1

After you updated question. Other answers provide you info about map

To answer why array and string differ look to constructors

String constructor accept 1 parameter String(thing) while array new Array(element0, element1[, ...[, elementN]])