To support sub-domain like en.wikipedia.org, we need to use en_wikipedia as body class to distinguish other language version of wikipedia. Similar, google translate should have different body class from gmail.

Bug fix:

If domain name consists of 2 or 3 labels, the code below won't work - it will return empty:

d_core = d_parts.slice(1, d_parts.length-1).join('_')

It's fixed as:

var d_core = d_parts[d_parts.length-2]
if (d_parts.length > 3){
d_core = d_parts.slice(1, d_parts.length-1).join('_')
}

Fix bug:
by using d_array.slice(start, end) - end is not included. That's different from node.js behavior.

If domain name consists of more than 3 labels, then use labels from 2nd to the one before last as the body class name. The dot will be replaced with underscore.
For example, if domain name is sandbox.gitlab.test.java.oracle.com, then use "gitlab_test_java_oracle" as body class.

By using domain name and top level domain are not necessary, and it will cause css misunderstanding the 'class' name as the dot '.' is special keyword for css class selector.

Thus, change to use domain name only as body class.

Fix domain name

Only choose last 2 parts in document.domain as domain name