Javascript Get Hostname of File Host

Question

Although this question is similar, it is not what I am looking for.

Let's say on HostA.com I include a script from HostB.com:

<script type="text/javascript" src="http://www.hostb.com/script.js">

When script.js runs, I need to get the name of HostB (let's assume it can change). If I use:

var hostName = window.location.hostname;

It will return HostA.com rather than HostB.com obviously because that is where the the window object is scoped.

How can I get the name of HostB from within the script? Do I have to locate the <script> element in the DOM and parse the src attribute or is there a better way?

EDIT

Yes, it is on my server, but may be on other servers as well. I am developing a javascript plugin and am trying to make absolute paths so it doesn't try to reference files on the server including the plugin.

If it's your server, you have access to that on the serverside, and can just output it into the script file that is served to the other site. — adeneo, Nov 12 '13 at 01:02
So you want to put code INSIDE the script from the other host that figures out what host it is on? — markasoftware, Nov 12 '13 at 01:06
You could access the script tag like so -> http://stackoverflow.com/questions/403967/how-may-i-reference-the-script-tag-that-loaded-the-currently-executing-script#answer-3326554 — adeneo, Nov 12 '13 at 01:07
@Markasoftware Yes. I'm using a CDN version of `require.js` to load a js file which contains plugin functionality. Some of it's dependencies require assets to be loaded and if I load them with relative paths, it assumes HostA rather than HostB (where the files are actually located). So I need to dynamically determine the hostname of HostB to avoid having to update the script anytime it is placed on a new server. — Jeremy Harris, Nov 12 '13 at 01:08

score 2 · Answer 1 · answered Nov 12 '13 at 01:16

2

Here is how: first off, include this as the first line of your script. I know it is a comment. Do it anyways

//BLAHBLAHBLAHBLAHAAABBBCCCDDDEEEFFFGGGILIKEPI

next, use this function inside of that script to determine the host

function findHost(){
    var scripts=document.getElementsByTagName('script');
    var thisScript=null;
    for(var i=0;i<scripts.length;i++){
        if(scripts[i].innerHTML.indexOf('//BLAHBLAHBLAHBLAHAAABBBCCCDDDEEEFFFGGGILIKEPI')!==-1)
            var thisScript=scripts[i];
    }
    var urlParser=document.createElement('a');
    urlParser.href=thisScript.getAttribute('src');
    return urlParser.hostname;
}

answered Nov 12 '13 at 01:16

markasoftware

12,292
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Interesting. Is this method more reliable than mine? – Jeremy Harris Nov 12 '13 at 01:21
no, it isn't, yours is probably better but I didn't know you were able to add attributes to your script. – markasoftware Nov 12 '13 at 01:23
This method is more reliable if you don't have any control over the code on hostA – dprothero Oct 01 '15 at 22:41

Jeremy Harris · Accepted Answer · 2013-11-12T01:38:52.517

I am loading the script with RequireJS which looks something like this:

<script data-main="http://hostb.com/js/app/main.js" src="http://hostb.com/js/vendor/require.js" type="text/javascript"></script>

I figured out, with help from @adeneo that I can do something like this:

$('script[data-main*="/js/app/main.js"]').attr('data-main')

Which returns:

http://hostb.com/js/app/main.js

And I can parse it for the hostname.

var url = $('script[data-main*="/main.js"]').attr('data-main');
parser = document.createElement('a');
parser.href = url;
host = parser.hostname;

Thanks for the suggestions and nudge in the right direction!

BREAKING NEWS

Turns out their is an easier way for anyone using RequireJS (who finds this question in search) and needs to be able to load absolute URL's with the script host:

var myCssPath = require.toUrl('css/mystyles.css');

That builds an absolute path using the hostname of the server running!

score 0 · Answer 3 · edited May 23 '17 at 11:55

To omit using the hostname twice (as you described in your 'accepted answer') I implemented the solution this as follows:

HTML on HostA.com:

<script data-main="my_embed_id" src="http://hostb.com/js/vendor/require.js" type="text/javascript"></script>

require.js on HostB.com:

// get host where this javascript runs
var url = $('script[data-main="my_embed_id"]').attr('src');
var hostb = url.replace(/(\/\/.*?\/).*/g, '$1');

Which returns:

http://hostb.com

Inspired by: How to make an external javascript file knows its own host?

Javascript Get Hostname of File Host

EDIT

3 Answers3

BREAKING NEWS