The keyword is &quot;well-tested, heavily used library&#x27;. Especially in the web area I see a lot of imported libraries from github or wherever for doing simple things. In the end you end up with dozens of dependencies you don&#x27;t know how and when to update.<p>My rule of thumb is if the stuff we need can be reduced to a few functions, it&#x27;s better to copy so you at least know which code you are using and don&#x27;t have thousands of lines of code in you repo where you don&#x27;t know if they are ever being used,