Javascript return only the subdomain part of a string url

Question

I have a string that is typically a url (minus the http/www part). Keep in mind this string is returned via an API and not parsed from the browser url.

For eg "xyz.abc.com or "login.xyz.abc.com"

Now I need to parse the string and return only the subdomain so that I get the following:

"xyz" and "login.xyz"

With Python, I can achieve this using the following code:

".".join(String.split(".")[:-2])

I am unable to find the appropriate syntax or equivalent in javascript.

not sure I understand the downvote. I could not find an answer for this in stack-overflow. also I provided a working example in python which means I tried to make this work, but couldnt do it in javascript — newbie
– newbie, Commented Oct 19, 2021 at 20:10
You can use almost the same code in Javascript: jsfiddle.net/kLvrtdzs — Alexandre
– Alexandre, Commented Oct 19, 2021 at 20:30

sjoerddt · Accepted Answer · 2021-10-19 20:19:14Z

2

If you're sure that the URL will always have a subdomain (it won't be just abc.com, for example), and that the top-level domain will always consist of one part (it won't be co.uk, for example), you could do this with the following JavaScript:

const exampleURL = "login.xyz.abc.com";
const splitURL = exampleURL.split(".");
const subdomains = splitURL.slice(0, splitURL.length - 2); // Remove the domain
const subdomainsString = subdomains.join(".")
console.log(subdomainsString)

However, keep in mind that the conditions I mentioned above are two pretty big ifs: if an URL is returned as example.co.uk, this method would think that example would be the subdomain.

answered Oct 19, 2021 at 20:19

sjoerddt

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1 Comment

Alexandre Over a year ago

Javascript's Array.prototype.slice can handle negative "end" index, so you could write just const subdomains = splitURL.slice(0, -2);.

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