Bitwise - Why 0 & 1 !== 1 & 1 return false in VSCode/Leetcode?-CodePudding

I was writing an algorithm to compare how many bits are different between 2 numbers using this function

 var hammingDistance = function(x, y) {
  let result = 0;
  while (x !== 0 || y !== 0) {
    // This line is incorrect
    if (x & 1 !== y & 1) result  ;
    x = x >> 1;
    y = y >> 1;
  }
  return result;
};

But my result is always 1 less than the correct answer, and it turns our my function is wrong when comparing the left most digit, such as 0011 and 0100. It returns 2 instead of 3.

https://i.imgur.com/P46RyZr.png

I can use XOR instead of !== to get the correct answer. But I'm wondering why?

CodePudding user response：

Your problem is that !== has a higher precedence than &. So your condition is actually (x & (1 !== y)) & 1. Use explicit grouping instead:

if ((x & 1) !== (y & 1)) result  ;

It works with ^ because that has a lower precedence than &.