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

2018-06-20 17:36:34

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

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

How do I fix this?

Number.prototype.mod = function(n) {
    return ((this%n)+n)%n;
};

采取这篇文章：JavaScript模块错误

Using Number.prototype is SLOW, because each time you use the prototype method your number is wrapped in an Object . Instead of this:

Number.prototype.mod = function(n) {
  return ((this % n) + n) % n;
}

Use:

function mod(n, m) {
  return ((n % m) + m) % m;
}

See: http://jsperf.com/negative-modulo/2

~97% faster than using prototype. If performance is of importance to you of course..

JavaScript中的%运算符是余数运算符，而不是模运算符（主要区别在于如何处理负数）：

-1 % 8 // -1, not 7

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