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Cache-Busting URL Builder

Append a stable version or content-hash query parameter to asset URLs without losing existing params or fragments.

JavascriptData Fetching

Code

snippet
// Cache-busting URL builder for static assets.
export function withCacheBusting(url, version, param = "v") {
  if (typeof url !== "string" || url.length === 0) {
    throw new TypeError("url must be a non-empty string");
  }
  if (!/^[A-Za-z_][A-Za-z0-9_-]*$/.test(param)) {
    throw new TypeError("param must be a valid query parameter name");
  }
  const base = "https://cache-busting.invalid";
  const parsed = new URL(url, base);
  if (parsed.protocol !== "https:" && parsed.protocol !== "http:") {
    throw new TypeError("only http(s) URLs are supported");
  }
  parsed.searchParams.set(param, String(version));
  if (parsed.origin === base) {
    return parsed.pathname + parsed.search + parsed.hash;
  }
  return parsed.toString();
}

export function hashAssetContent(content) {
  let hash = 0x811c9dc5;
  const text = String(content);
  for (let index = 0; index < text.length; index += 1) {
    hash ^= text.charCodeAt(index);
    hash = Math.imul(hash, 0x01000193);
  }
  return (hash >>> 0).toString(36);
}

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