I've got a really big number: 5799218898. And want to shift it right to 13 bits.
So, windows-calculator or python gives me:
5799218898 >> 13 | 100010100100001110011111100001 >> 13 70791 | 10001010010000111
As expected.
But Javascript:
5799218898 >> 13 | 100010100100001110011111100001 >> 13 183624 | 101100110101001000
I think it because of internal integer representation in javascript, but cannot find anything about that.
In ECMAScript (Javascript) bitwise operations are always in 32-bit. Therefore 5799218898 is chopped into 32-bit which becomes 1504251602. This integer >> 13 gives 183624.
In Python they are arbitrary-length integers. So there's no problem.
(And the numbers in Windows calculator are 64-bit, enough to fit 5799218898.)
(And the correct answer should be 707912.)
The number you have (5799218898) is beyond 32 bits. You didn't mention the JavaScript engine you're testing with, but it's very likely that it is 32-bit.
To test, trim the "5" at the beginning of your number so that you fall inside the 32-bit boundary. Then your shift should work fine.
As Nicholas Zakas states:
Even though JavaScript numbers are technically stored in 64-bits, integer values are treated as if they’re 32 bits whenever bitwise operators are involved.
来源：https://stackoverflow.com/questions/2373791/bitshift-in-javascript