Is there a best practice to validating user input links?

Question

I have a text input field that once entered by the user we will be converting to an external hyperlink using the safeLink function. We are trying to figure how best to validate the contents of the text input field since safeLink doesnt work unless the enters http: or https: (if they do not enter in the http/https the formula redirects to a nonexistent Appian record vs URL). 
 
 Since the user may also be putting in links to intranet pages(SharePoint, local repositories, etc.), does anyone have an effective method for validating that text input values are valid external URLs outside of simply validating that the contents contain http/https? 
 
 Thanks in advance!

JarrodSharp · Answer

I'd suggest using a regular expression test to validate the input. There are available functions in a shared component "Appian Regular Expression" functions. Then a quick search of the internet reveals a few URL regex patterns which might do the job, such as: 
 https://www.regexpal.com/94502 or 
 stackoverflow.com/.../what-is-the-best-regular-expression-to-check-if-a-string-is-a-valid-url 
 
These won't be able to validate that the endpoint actually is live however