Javascript 十进制到二进制 - 64 位

问题描述

十进制-805306368的二进制是:

The binary for the decimal -805306368 is:

1111111111111111111111111111111 11010000000000000000000000000000

11111111111111111111111111111111 11010000000000000000000000000000

但是，在 Javascript 中，我得到 以下:

However, in Javascript I get the following:

   var str = parseInt(-805306368).toString(2);
   document.write(str);

-110000000000000000000000000000

-110000000000000000000000000000

谁能解释一下如何解析这个十进制的 64 位二进制字符串?

Can anyone explain how to parse the 64 bit binary string from this decimal?

推荐答案

JavaScript 不使用补码表示，它在字符串前面使用 - 字符.那是因为它不知道你的数字范围有多少位.

JavaScript does not use the two's-complement representation, it uses a - character in front of the string. That's because it does not know how many bits your number range has.

要获得预期的结果，您可以反转每个位:

To get the expected result, you could invert each bit:

>>> (~-805306368).toString(2)
"101111111111111111111111111111"

然而，javascript 对 32 位整数执行所有二进制操作，因此这不适用于更大(或更小)的数字，并且至少会非常混乱.因此，您需要实现自己的格式化算法.

Yet, javascript does all binary operations on 32-bit integers, so this won't work for bigger (or smaller) numbers and at least will be very confusing. So, you would need to implement your own formatting algorithm.

// example of to 32-bit-conversion:
>>> (~parseInt("1111111111111111111111111111111",2)).toString(2)
"-10000000000000000000000000000000"
>>> (~parseInt("11111111111111111111111111111111",2)).toString(2)
"0"

我的实现:

String.prototype.padleft = function(len, chr){...}

function get64binary(int) {
    if (int>=0)
        return int
          .toString(2)
          .padleft(64, "0");
    // else
    return (-int-1)
      .toString(2)
      .replace(/[01]/g, function(d){return +!+d;}) // hehe: inverts each char
      .padleft(64, "1");
}

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