With her Harry Potter stage play about to debut in London's West End, J.K. Rowling has once again demonstrated her level-headed approach to dealing with the internet's haters.Set 19 years after the final novel, Harry Potter and the Cursed Child introduces new, older versions of the much-loved characters Harry, Hermione and Ron. Though many fans were excited when Olivier Award-winning actress Noma Dumezweni was cast as Hermione, a small number took issue with the idea of a black woman playing the character portrayed in the films by Emma Watson."With my experience of social media, I thought that idiots were going to idiot," Rowling, who has 7.4 million Twitter followers, told The Observer . "But what can you say? That’s the way the world is. Noma was chosen because she was the best actress for the job. When John told me he'd cast her, I said, 'Oh, that's fabulous' because I’d seen her in a workshop and she was fabulous."Rowling then explained that she refused to let any casting criticism drag her down. "I had a bunch of racists telling me that because Hermione ‘turned white’ – that is, lost colour from her face after a shock – that she must be a white woman, which I have a great deal of difficulty with," she recalled to The Observer . "But I decided not to get too agitated about it and simply state quite firmly that Hermione can be a black woman with my absolute blessing and enthusiasm."Previews of Harry Potter and the Cursed Child, an ambitious story told over two parts, begin this week at London's Palace Theatre. The two-part play then opens officially in July.If you haven't managed to buy tickets yet, it's not necessarily too late. Every Friday at 1pm, 40 tickets for the following week's shows will be made available at a special lower price on the play's website . Good luck!