It's also worth mentioning that copying and pasting from within the same project is also a no-no. It's a source of considerable technical debt and it WILL bite you later on when you need to update the functionality. It's always a good use of time to make that functionality reusable properly rather than just carelessly copying and pasting it. If you're rushing to get something live when under the gun, you can justify it, but only if you make sure you go back later and refactor it.
Relevant article from BBC News.
It's also worth mentioning that copying and pasting from within the same project is also a no-no. It's a source of considerable technical debt and it WILL bite you later on when you need to update the functionality. It's always a good use of time to make that functionality reusable properly rather than just carelessly copying and pasting it. If you're rushing to get something live when under the gun, you can justify it, but only if you make sure you go back later and refactor it.