I am new here and don't understand why my question Fast js datagrid for ipad was closed? I saw "what js library is good for x" questions many times here. Is it no longer a good question for stackoverflow or this is because of poor formatting?
As psubsee points out, questions that "shop" for things, like code or libraries, aren't really the best questions for Stack Overflow. Instead, the best questions are those that show research effort, have code examples, and describe a problem.
In your question, you're asking someone to give you code or give you a link to code that solves your problem. Instead, consider that the experts that can solve your problem are here, not somewhere else. So one thing you could do to possibly get your question reopened would be to edit it and instead focus on the problem you're facing.
Dig a little deeper. What is the problem you're trying to solve. Show your code. Ask how you can improve the performance. If the answers happen to be "use this datagrid library, oh and by the way, here's an example" then so be it, but questions on Stack Overflow shouldn't just outright ask for code.
For further reading, see Q&A is Hard, Let's Go Shopping.
I can't emphasize enough how I think that you really do have a good question buried in there waiting to be uncovered with some edits! Hope this helps!
Questions like this would result in not ending discussions about what is better. These subjective questions have no place in SO. It is just solve the issue that encounters.