Is it OK if i leave my iPhone 5s charging for a hole night?

It is fine.

It is quite OK to leave the charger connected overnight. Charging stops when the battery reaches 100%.

I have done it with my 5s and the other I have had before 3-4-5

with no problem.

Mike

You can let it charge for a whole night or any length of time. Doing so does not harm the battery.

I've had iPhones since the 2nd day they became available 7 years ago. I plug in the phone when I go to bed, unplug it in the morning. I have never missed a day night in those 7 years, and it hasn't hurt any of my phones.

Think about what you're asking for a second... Do you really think any reputable company that produces a product designed to run on a battery would sell something that would be damaged simply by charging that battery? There would be class action lawsuits left and right and Apple would be outa business.