Validate manual URL entry

I have a url where the last character or characters has to be a number after the last / in the url page. Everything works great where the last character/s is always a number after the final / in the URL:
[url]http://myserver:8080/mypage/2[/url]
or
[url]http://myserver:8080/mypage/4[/url]
or
[url]http://myserver:8080/mypage/12[/url]

Sometimes a user will manually enter the url in their Browser and put a non Integer at the end of the url where it should only be a Integer:
[url]http://myserver:8080/mypage/ab[/url]
or
[url]http://myserver:8080/mypage/4g[/url]

This gives an error message and I was hoping to create something in JavaScript to give a customized error page or redirect to a customized error page. The main thing is I dont want the Server side error message to show when someone puts in an invalid URL entry with non integer number after the last / in the url.

Please advise how I can handle this using JavaScript?

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