Why does JavaScript split() produce different output with different variable names?

Question

Following is some codes and output from the Chrome Developers\' Console

Case 1:

var myarr = document.location.hostname.split(\".\");         


        

Answer 1

James is right: because name is a string property of window, if you're executing this code in the global scope you're set that property not your variable. So, if you set an array, it set to window.name the string version of that array (basically, array.toString() that is the same of array.join()).

Because it's a string – and not an array – using the square notation let you access to the single character based on a specific index. So:

var str = "ptamz";
str[0] // "p"
str[1] // "t"

It's equivalent to:

var str = "ptamz";
str.charAt(0) // "p"
str.charAt(1) // "t"

Answer 2

name is a property of window. It appears that when you try to set that property to an array, the keys are joined with a comma (the result of calling toString on an array). So you are actually setting the window.name property to the concatenation of each element of document.location.hostname.split("."), separated by commas.

Here's a screenshot from my Chrome console demonstrating what happens:

The reason name[0] then results in p is that you can access the characters of strings using square brackets:

name = "hello,world";
console.log(name[0]); //"h"

Edit

As others have mentioned, this will only be the case in the global scope. You are free to declare a variable named name inside a descendant scope. Although, obviously, omitting the var keyword in this case would still result in you accessing window.name:

function example() {
    var name = ["hello", "world"];
    console.log(name); //["hello", "world"]
}

Answer 3

name in global scope is an empty string, so in the latter case you get the array returned by split transformed into a string "www,hostname,com". So name[0] gets you the first letter only.