`parseInt` takes two arguments, the string to parse and an optional radix. (or base)
`Array.prototype.map` takes a function and calls that function for each element in the array, passing in the value, the index, and the array itself.
That means that your 0th element will be parsed as you would expect, your 1st element will be parsed as gibberish, your 2nd element will be parsed as base 2, your 6th element will be parsed as base 6, etc....
I have never seen a browser that requires the radix, and MDN specifically calls out that you should pass both arguments or you will get unexpected results. They wouldn't need to do that if the radix was required.
Now, should you treat the radix as optional? Absolutely not. I've got several commits on newly adopted codebases where I went through and explicitly used `10` as the radix anywhere `parseInt` was called. But is it technically optional? Absolutely.
`Array.prototype.map` takes a function and calls that function for each element in the array, passing in the value, the index, and the array itself.
That means that your 0th element will be parsed as you would expect, your 1st element will be parsed as gibberish, your 2nd element will be parsed as base 2, your 6th element will be parsed as base 6, etc....