Checking whether the result of a bitwise operation is greater than zero may yield unexpected results due to arithmetic overflow.

It is more robust to check whether the result of the bitwise operation is non-zero.

In the following example, function bitIsSet is meant to implement a check whether the nth bit of value x is set.

However, this check fails to produce the correct value when x is set to -1 (that is, all its bits are ones), and n is set to 31: in this case, the expression x & (1<<n) evaluates to -2147483648. So the function returns false, even though the 31st bit of x is, in fact, set.

To account for this edge case, bitIsSet should be rewritten like this:

Mozilla Developer Network: Bitwise operators.