Comment by vanderZwan | Hacker News Reader

Comment by vanderZwan | Hacker News Reader

In the previous discussion someone lamented they wished they could do this in JavaScript[0].

Nowadays we have TextDecoder and BigInt64Array so I'm pretty sure we actually could do it[1][2].

I doubt it would be faster than calling <number>.toString(2), but in principle we could port this.

[0] https://news.ycombinator.com/item?id=10517332

[1] https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder

[2] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

Here we go:

    const toBinary = (() => {
      const u64 = new BigUint64Array(1);
      const u8 = new Uint8Array(u64.buffer)
      u8[0] = 255;
      const decoder = new TextDecoder();
    
      return (number) => {
        u64[0] = 0n;
        u8[0] = number;  // We're assuming little-endian architectures
        u64[0] = (((u64[0] * 0x8040201008040201n) >> 7n) & 0x0101010101010101n) + 0x3030303030303030n
        return decoder.decode(u8)
      };
    })()

<number>.toString(2) Wouldn't be quite right because the output needs to be padded out with zeros.

Oh, right, good catch! So <number>.toString(2).padStart(8, "0") then. I still expect it to be faster than this clever hack though.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

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