HTMLs/BV.html

<!DOCTYPE html> 
<html>
<head>
  <meta charset="UTF-8">
  <title>Bilibili AV/BV 号转换</title>

<script>
function* withIndex(xs) {
  let i = 0;
  for (let x of xs) yield [i++, x];
}
function makeReversedIndex(xs) {
  let reverseIndex = {};
  for (let [i, x] of withIndex(xs)) reverseIndex[x] = i;
  return reverseIndex;
}
const div = (a, b) => Math.floor(a / b);
const compose = (f, g) => x => f(g(x));

const helem = id => document.getElementById(id);
function updateFrequency(delay_ms, op) {
  let timerId = null;
  return (...args) => {
    clearTimeout(timerId);
    setTimeout(op.bind(null, args), delay_ms);
  };
}
</script>

<script>
const table = "fZodR9XQDSUm21yCkr6zBqiveYah8bt4xsWpHnJE7jL5VG3guMTKNPAwcF";
const tableFind = makeReversedIndex(table);

const
  TEMPLATE = "BV1  4 1 7  ",
  BLANK = [11,10,3,8,4,6],
  AV_XOR = 0xa93b324,
  AV_ADD = 0x2084007c0;

function bvFrom(av) {
  let avHash = (av^AV_XOR) + AV_ADD;
  let res = [...TEMPLATE];
  for (let [i, x] of withIndex(BLANK)) {
    const k = table.length;
    res[x] = table[div(avHash, (k**i)) % k];
  }
  return res.join("");
}
function bvTo(bv) {
  let res = 0;
  const k = table.length;
  for (let [i, x] of withIndex(BLANK)) {
    res += tableFind[bv[x]] * (k**i)
  }
  return (res - AV_ADD) ^ AV_XOR;
}
const
  bvVerify = compose(bvTo, bvFrom),
  bvVerifyBack = compose(bvFrom, bvTo);
</script>
</head>

<body>
  <h3 class="header">Bilibili AV/BV 视频编号转换</h3>
  <input id="video-code" placeholder="视频编号，如 BV17x411w7KC 或 170001"></input>
  <div id="code-trans"></div>
  <div id="code-trans-extra"></div>
<script>
const
  input = helem("video-code"),
  output = helem("code-trans"),
  extra = helem("code-trans-extra");
const
  regexBV = /^BV[0-9A-Za-z]{10}$/,
  regexAV = /^\d+$/;

input.oninput = updateFrequency(300, () => {
  let text = input.value;
  let verified = false;
  if (regexBV.test(text)) {
    output.innerText = bvTo(text);
    verified = bvVerifyBack(text) == text;
  } else if (regexAV.test(text)) {
    output.innerText = bvFrom(text);
    verified = bvVerify(text) == text;
  } else {
    extra.innerText = "（无法解析新输入）";
    return;
  }
  extra.innerText = verified? "（OK）" : "（好像有问题）";
});
</script>

<style>
html {
  background: #efefef;
}
body {
  max-width: 800px;
  margin: 0 auto;
}
.header {
  text-align: center;
  padding: 60px 0;
}

</style>
</body>
</html>