https://twitter.com/needle/status/1466336299703422977 の文字化けを解読する時に使ったスクリプト

mojibake.js

function* range(a, b) {
  for (let i = a; i <= b; i++) {
    yield i;
  }
}

function* decode(s) {
  const b = Buffer.from(s, "latin1");
  if (b.length === 1) {
    for (const i of range(0x80, 0x9f)) {
      for (const j of range(0x80, 0x9f)) {
        yield [b[0], i, j];
      }
    }
  } else if (b.length === 2) {
    for (const i of range(0x80, 0x9f)) {
      yield [b[0], i, b[1]];
      yield [b[0], b[1], i];
    }
  }
}

const d = "å»ä¸ãªãã³ã°å´"
  .match(/[\x00-\x7f]|[\xc0-\xff][\x80-\xbf]*/g)
  .map(s => Array.from(decode(s)).map(a => Buffer.from(a).toString()).join(""));
for (const i of d) {
  console.log(i);
}