Include common js file

Hi everyone,
I've only recently starting with asp .net. One thing I've often wanted to do was to have and maintain a common javascript file across all my different web apps. Is there a way I can have a js file in some location outside the VS web app folder which all my web apps can link to? That way I can maintain that js file and all the web apps will simply include any updates next time I build them. Currently I copy the js to each web app.
Regards,
Mark.
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