JavaScript % (modulo) gives a negative result for negative numbers

Question

According to Google Calculator (-13) % 64 is 51.

According to Javascript (see this JSBin) it is -13.

How do I fix this

Answer 1

If x is an integer and n is a power of 2, you can use x & (n - 1) instead of x % n.

> -13 & (64 - 1)
51