bilibili/flv.js · error · InvalidArgumentException

Invalid seekType in config: ${config.seekType}

Error message

Invalid seekType in config: ${config.seekType}

What it means

IOController._selectSeekHandler accepts only known seekType values ('range', 'param', 'custom'); anything else reaches the final else branch and throws an InvalidArgumentException naming the invalid value. It prevents silent misconfiguration of how range requests are built.

Source

Thrown at src/io/io-controller.js:235

    }

    _selectSeekHandler() {
        let config = this._config;

        if (config.seekType === 'range') {
            this._seekHandler = new RangeSeekHandler(this._config.rangeLoadZeroStart);
        } else if (config.seekType === 'param') {
            let paramStart = config.seekParamStart || 'bstart';
            let paramEnd = config.seekParamEnd || 'bend';

            this._seekHandler = new ParamSeekHandler(paramStart, paramEnd);
        } else if (config.seekType === 'custom') {
            if (typeof config.customSeekHandler !== 'function') {
                throw new InvalidArgumentException('Custom seekType specified in config but invalid customSeekHandler!');
            }
            this._seekHandler = new config.customSeekHandler();
        } else {
            throw new InvalidArgumentException(`Invalid seekType in config: ${config.seekType}`);
        }
    }

    _selectLoader() {
        if (this._config.customLoader != null) {
            this._loaderClass = this._config.customLoader;
        } else if (this._isWebSocketURL) {
            this._loaderClass = WebSocketLoader;
        } else if (FetchStreamLoader.isSupported()) {
            this._loaderClass = FetchStreamLoader;
        } else if (MozChunkedLoader.isSupported()) {
            this._loaderClass = MozChunkedLoader;
        } else if (RangeLoader.isSupported()) {
            this._loaderClass = RangeLoader;
        } else {
            throw new RuntimeException('Your browser doesn\'t support xhr with arraybuffer responseType!');
        }
    }

View on GitHub (pinned to 42343088f2)

Solutions

  1. Set seekType to one of 'range' | 'param' | 'custom'
  2. Log/inspect config.seekType before constructing to catch bad values from dynamic config sources
  3. Use 'range' (Range requests via Range header) as the default for progressive media
  4. If custom behavior is needed, use seekType:'custom' with a valid customSeekHandler

Example fix

// before
const config = { seekType: 'byterange' }; // throws InvalidArgumentException
// after
const config = { seekType: 'range' };
Defensive patterns

Strategy: validation

Validate before calling

const VALID_SEEK_TYPES = ['range', 'param', 'custom'];
if (!VALID_SEEK_TYPES.includes(config.seekType)) {
  throw new TypeError(`seekType must be one of ${VALID_SEEK_TYPES}, got: ${config.seekType}`);
}

Type guard

const isValidSeekType = (t) => t === 'range' || t === 'param' || t === 'custom';

Try / catch

try {
  const controller = new IOController(loaderClass, config, extraData);
} catch (e) {
  if (e instanceof InvalidArgumentException && /Invalid seekType/.test(e.message)) {
    config.seekType = 'range';
  }
}

Prevention

When it happens

Trigger: Instantiating IOController with config.seekType set to a misspelled or unsupported string such as 'Range', 'bytes', 'params', or left as an arbitrary value from user input.

Common situations: Typo in the config value, configuration loaded from JSON/user settings with an unexpected string, upgrading the library and using a seekType that was never supported, camelCase/kebab-case mismatches ('chunked', 'byterange').

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of bilibili/flv.js@42343088f2 (2026-09-01). Data as JSON: /api/errors/ff3c30961b5efd03. Report an issue: GitHub.