How to extract the host from a URL in JavaScript?

Question

Capture the domain till the ending characters $, \?, /, :. I need a regex that captures example.com in all of these.

example.com:3000
example.com?pass=gas
example.com/
example.com

@macek I built a URL / URI builder for javascript that takes arguments and constructs the URL from an object. I'm looking to create a regular expression that can take a string and create the object. stackoverflow.com/questions/13498417/build-urls-from-json — ThomasReggi
– ThomasReggi, Commented Nov 22, 2012 at 5:50

Stephen Ostermiller · Accepted Answer · 2022-07-01 22:46:04Z

57

If you actually have valid URLs, this will work:

var urls = [
    'http://example.com:3000',
    'http://example.com?pass=gas',
    'http://example.com/',
    'http://example.com'
];

for (x in urls) {
    var a = document.createElement('a');
    a.href = urls[x];
    console.log(a.hostname);
}

//=> example.com
//=> example.com
//=> example.com
//=> example.com

Note, using regex for this kind of thing is silly when the language you're using has other built-in methods.

Other properties available on A elements.

var a = document.createElement('a');
a.href = "http://example.com:3000/path/to/something?query=string#fragment"

a.protocol   //=> http:
a.hostname   //=> example.com
a.port       //=> 3000
a.pathname   //=> /path/to/something
a.search     //=> ?query=string
a.hash       //=> #fragment
a.host       //=> example.com:3000

EDIT #2

Upon further consideration, I looked into the Node.js docs and found this little gem: url#parse

The code above can be rewritten as:

var url = require('url');

var urls = [
    'http://example.com:3000',
    'http://example.com?pass=gas',
    'http://example.com/',
    'http://example.com'
];

for (x in urls) {
    console.log(url.parse(urls[x]).hostname);
}

//=> example.com
//=> example.com
//=> example.com
//=> example.com

EDIT #1

See the revision history of this post if you'd like to see how to solve this problem using jsdom and nodejs

edited Jul 1, 2022 at 22:46

Stephen Ostermiller♦

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answered Nov 22, 2012 at 5:40

maček

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11 Comments

ThomasReggi Over a year ago

javascript but I would really just like a regex

ThomasReggi Over a year ago

This would be great, but I'm working server-side. No doc =[. Might be a way to fake it.

maček Over a year ago

Have you heard of jsdom? Also, you should've mentioned you were using something like node.js in the tags :P

maček Over a year ago

@ThomasReggi, I discovered that nodejs has it's own url#parse method. Please see Edit #2 above.

stroncium Over a year ago

Using DOM objects is not JS feature, but DOM binding feature. DOM doesn't exist in many JS environments. Also, it is very slow, and the proper way to perform simple string parsing is EXACTLY using regexps.

|

Stephen Ostermiller · Accepted Answer · 2022-07-01 22:47:16Z

32

Since you're using node, just use the built-in url.parse() method; you want the resulting hostname property:

var url=require('url');
var urls = [
  'http://example.com:3000',
  'http://example.com?pass=gas',
  'http://example.com/',
  'http://example.com'
];

urls.forEach(function(x) {
  console.log(url.parse(x).hostname);
});

edited Jul 1, 2022 at 22:47

Stephen Ostermiller♦

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answered Nov 22, 2012 at 7:10

ebohlman

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4 Comments

ThomasReggi Over a year ago

returns

{ pathname: '0', path: '0', href: '0' } { pathname: '1', path: '1', href: '1' } { pathname: '2', path: '2', href: '2' } { pathname: '3', path: '3', href: '3' }

ebohlman Over a year ago

Goofed-up test harness (copied from another answer), updated in my answer. Lesson: don't use for (...in...) to iterate over arrays.

Muhammad Umer Over a year ago

it includes subdomain

Jakub Keller Over a year ago

@MuhammadUmer subdomain is part of the hostname.

Paul Weber · Accepted Answer · 2018-05-18 12:34:42Z

28

A new challenger has appeared. According to node docs, you can also use

   var url = new URL(urlString);
   console.log(url.hostname);

https://nodejs.org/api/url.html#url_the_whatwg_url_api

This seems to be a more current way.

answered May 18, 2018 at 12:34

Paul Weber

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Comments

rb- · Accepted Answer · 2019-05-21 15:18:23Z

6

I'm using Node ^10 and this is how I extract the hostname from a URL.

var url = URL.parse('https://stackoverflow.com/q/13506460/2535178')
console.log(url.hostname)
//=> stackoverflow.com

edited May 21, 2019 at 15:18

answered Aug 25, 2018 at 15:36

rb-

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Comments

ThomasReggi · Accepted Answer · 2023-01-02 22:10:32Z

1

I reccomend using the new URL class that is now included in most browsers.

var urls = [
  'http://example.com:3000',
  'http://example.com?pass=gas',
  'http://example.com/',
  'http://example.com'
];

urls.forEach(url => {
  const u = new URL(url)
  console.log(u.hostname)
})

answered Jan 2, 2023 at 22:10

ThomasReggi

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Comments

stroncium · Accepted Answer · 2013-04-19 08:35:24Z

0

/^((?:[a-z0-9-_]+\.)*[a-z0-9-_]+\.?)(?::([0-9]+))?(.*)$/i

matches are host, port, path

answered Apr 19, 2013 at 8:35

stroncium

1,4319 silver badges8 bronze badges

4 Comments

xShirase Over a year ago

Does not work : s="stackoverflow.com/questions/13506460/…" s.match(/^((?:[a-z0-9-]+\.)*[a-z0-9-]+\.?)(?::([0-9]+))?(.*)$/i) gives the following result : ["stackoverflow.com/questions/13506460/…", "http", undefined, "://stackoverflow.com/questions/13506460/how-to-extract-the-host-from-a-url-in-javascript"]

stroncium Over a year ago

Don't post fake test please. Your results contain string "http" as a matched string while the string you say you run regexp on doesn't contain "http" substring. You either patched the execution result or source code of your jS virtual machine to achieve this results. "stackoverflow.com/questions/13506460/how-to-extract...".match(/^((?:[a-z0-9-]+\.)*[a-z0-9-]+\.?)(?::([0-9]+))?(.*)$/i) works perfectly fine resulting in

["stackoverflow.com/questions/13506460/how-to-extract...", "stackoverflow.com", undefined, "/questions/13506460/how-to-extract..."]

xShirase Over a year ago

nope, stackoverflow auto cuts the url... Now, please check this fiddle : jsfiddle.net/WLGmv and let me know if I'm doing anything wrong.

stroncium Over a year ago

Sure thing. You try to use this regexp for the wrong purpose. If you reread the original question, it was not supposed to do what you want. You need to parse URLs with URI scheme, try this: /^(?:https?:\/\/)?((?:[a-z0-9-_]+\.)*[a-z0-9-_]+\.?)(?::([0-9]+))?(.*)$/i (works only for http and https or no URI scheme at all). Fiddle is here: jsfiddle.net/WLGmv/1

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