如何从javascript中的大量数字中计数? [英] How could I count bit from large number in javascript?

问题描述

我有很多存储在字符串中.

I have a large number stored in string.

let txt = '10000000000000041';

所以我怎么计数以二进制格式显示的位.例如，9的二进制格式是1001，而1的二进制数都不是2.

So how could I count bit presenting in it's a binary format. for example, the binary format of 9 is 1001, and no of 1's is 2.

我到目前为止所做的:

const countOne = (num) => {
  let c = 0;
  while (num > 0) {
    num &= num - 1;
    c++;
  }
  return c;
}

console.log(countOne(+'9'));
console.log(countOne(+'10000000000000041'));

此代码可以正常工作，但不能实现较大的值，因为JavaScript中的Number无法容纳如此大的值，因此给出了错误的答案.

This code is working fine, but not for large value, because Number in JavaScript cannot hold such large value, so it's giving the wrong answer.

我发现了类似的问题，但不是很有价值.

I found similar questions but not for large value.

推荐答案

在较新的引擎(至少是Chrome，FF，Opera和Node)中，请参见

In newer engines (Chrome, FF, Opera, and Node at least, see compatibility table), just cast to a BigInt first:

let txt='10000000000000041';
const countOne = (num) => {
  let c = 0;
  while (num > 0) {
    num &= num - 1n;
    c++;
  }
  return c;
}
console.log(countOne(BigInt(txt)));
console.log(countOne(BigInt(1)));
console.log(countOne(BigInt(2)));
console.log(countOne(BigInt(3)));
console.log(countOne(BigInt(4)));
console.log(countOne(BigInt(5)));
console.log(countOne(BigInt(6)));
console.log(countOne(BigInt(7)));

<script>
try {
  eval('1n');
} catch(e) {
  throw "Your browser doesn't support BigInt syntax yet";
}
</script>

10000000000000041以二进制是 100011100001101111001001101111110000010000000000101001 ，因此23是正确的:

10000000000000041 in binary is 100011100001101111001001101111110000010000000000101001, so 23 is correct:

console.log(
  [...'100011100001101111001001101111110000010000000000101001']
  .reduce((a, b) => a + (b === '1'), 0)
);

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