Here’s a quick list of social sharing links to use on custom buttons. No need for JavaScript, heavy libraries or giving away your data by using Facebook’s Share button. Just replace each variable (URL, TEXT, etc).
<a href="https://www.facebook.com/sharer/sharer.php?u=URL">Share on Facebook</a>
<a href="https://twitter.com/intent/tweet?url=URL&text=TEXT">Share on Twitter</a>
<a href="http://www.reddit.com/submit?url=URL&title=TEXT">Share on Reddit</a>
<a href="https://pinterest.com/pin/create/button/?url=URL&media=&description=TEXT">Share on Pinterest</a>
<a href="https://www.linkedin.com/shareArticle?mini=true&url=URL">Share on Linkedin</a>
Bonus: Email
<a href="mailto:[email protected]?&subject=SUBJECT&[email protected]&[email protected]&body=URL%0ATEXT">Send by email</a>