javascript - 在 javascript 中设置第 31 位是否正确？

Question

当我尝试设置 31 位时 0 | 1 << 31我得到以下结果:

console.log(0 | 1 << 31); // -2147483648

实际上是:

console.log((-2147483648).toString(2)) // -10000000000000000000000000000000

设置 31 位是否正确，或者我应该限制为 30以防止负值？

Answer 1

引用 ECMA5 按位运算符和移位运算符对 32 位整数进行运算，因此在这种情况下，最大安全整数为 2^31-1，即 2147483647。

这是一个explanation .

The << operator is defined as working on signed 32-bit integers (converted from the native Number storage of double-precision float). So 1<<31 must result in a negative number.

The only JavaScript operator that works using unsigned 32-bit integers is >>>. You can exploit this to convert a signed-integer-in-Number you've been working on with the other bitwise operators to an unsigned-integer-in-Number:

(1<<31)>>>0