​ Accessing Arrays with Named Indexes problem

[dgvirtual]

I was fiddling with „Accessing Arrays with Named Indexes“ section examples of the Javascript tutorial and run into a situation I cannot understand. 

In short, I create an array 'person', then add elements to the array by index, and then add a third element by name. According to the tutorial, this should convert the array to an object (see here: https://www.w3schools.com/js/js_mistakes.asp) . Instead, after this I can access the variable 'person' as both an array (with two elements) and an object (or rather, a person.age property of the object). typeof 'person' reports: object.

var person = [];
person[0] = "John";
person[1] = "Doe";
person["age"] = 46;

Here is a link to the full test: https://www.w3schools.com/code/tryit.asp?filename=GHWDV13H8E0Z

Could someone explain what is happening here?