divisible-by-9

Divisible by 9?

Given a non-negative integer number represented as a string, which can be arbitrary large. Detect whether it is divisible by 9?

e.g

0 -> true  
7 -> false  
9 -> true  
18 -> true  
19 -> false  
777777777777777777777777777777777777777777777 -> true

Tips:

• All input strings in the tests are valid non-negative integer numbers, you don't have to check that.
• You'd better not use the arbitrary-precision data types from chosen programming languages, if any, to keep the kata fun :)
  • For Java, avoid BigInteger or BigDecimal.
  • For Javascript, avoid BigInt.
  • For Python3, since int has unbounded range, so avoid converting the whole input as a single int directly.
  • etc ...