The Harry Potter creator turns 50 on 31 July (15), and she's planning a big party.

She tells U.S. breakfast show Today, "My mother died at 45... You've got to celebrate every year that you are here and in good health because what's the alternative? What's the alternative to ageing? It's checking out and I'd rather still be here.

"I still have children to raise, I still have books to write. So genuinely I will have a party with my friends, we'll have a great time. I'm looking forward to it."