You can get kits for sliding closet doors but they can be expensive ($500 – $1,000) and the doors are usually the hollow, light doors which can lead to problems sliding smoothly and issues if you have to trim them to the closet size. I usually like to buy a heavy duty bracket and rail because it allows me to use a real wooden door, which is heavier, slides smoother, lasts longer and is easier to trim. All good reasons I figure.
Here’s a recent job where the doors had to be trimmed and the entire frame shimmed out to make it square and plumb. Just have to add a couple of handles and paint now.