bilibili/flv.js · error · InvalidArgumentException

Url must be a non-empty string!

Error message

Url must be a non-empty string!

What it means

IOController.updateUrl() validates its argument before assigning it to the internal data source URL. The library throws InvalidArgumentException when the url is falsy, not a string, or an empty string, because a subsequent load with an invalid URL could never succeed. It is a defensive API-contract check for the caller.

Source

Thrown at src/io/io-controller.js:354

        this._loader.destroy();
        this._loader = null;

        let requestRange = {from: bytes, to: -1};
        this._currentRange = {from: requestRange.from, to: -1};

        this._speedSampler.reset();
        this._stashSize = this._stashInitialSize;
        this._createLoader();
        this._loader.open(this._dataSource, requestRange);

        if (this._onSeeked) {
            this._onSeeked();
        }
    }

    updateUrl(url) {
        if (!url || typeof url !== 'string' || url.length === 0) {
            throw new InvalidArgumentException('Url must be a non-empty string!');
        }

        this._dataSource.url = url;

        // TODO: replace with new url
    }

    _expandBuffer(expectedBytes) {
        let bufferNewSize = this._stashSize;
        while (bufferNewSize + 1024 * 1024 * 1 < expectedBytes) {
            bufferNewSize *= 2;
        }

        bufferNewSize += 1024 * 1024 * 1;  // bufferSize = stashSize + 1MB
        if (bufferNewSize === this._bufferSize) {
            return;
        }

View on GitHub (pinned to 42343088f2)

Solutions

1. Pass a non-empty string to updateUrl, e.g. updateUrl(String(newUrl)).
2. Coerce or validate the value first: if (typeof newUrl === 'string' && newUrl.length > 0) controller.updateUrl(newUrl).
3. Check where the URL originates (config, API response) and fix the empty/undefined source.

Example fix

// before
controller.updateUrl(urlFromServer);
// after
if (typeof urlFromServer === 'string' && urlFromServer.length > 0) {
    controller.updateUrl(urlFromServer);
}

function canUpdateUrl(url) {
    return typeof url === 'string' && url.length > 0;
}
if (canUpdateUrl(newUrl)) ioController.updateUrl(newUrl);

function isNonEmptyString(v) {
    return typeof v === 'string' && v.length > 0;
}

try {
    ioController.updateUrl(candidate);
} catch (e) {
    if (e.name === 'InvalidArgumentException') console.warn('Invalid URL skipped:', candidate);
    else throw e;
}

When it happens

Trigger: Calling ioController.updateUrl(undefined), updateUrl(null), updateUrl(''), or updateUrl(123) / any non-string value. Only IOController.updateUrl(src/io/io-controller.js:354) throws it.

Common situations: Passing a variable that was never populated (e.g. a URL fetched asynchronously that came back empty), reading a config field that is undefined, or accidentally passing a URL object instead of a string.

Understand the failure class

Background: "must be a positive integer", "cannot be empty", "invalid argument": how invalid-argument errors work across open-source libraries — this error's family across 33 libraries.

Related errors

• FlvPlayer requires an flv MediaDataSource input!
• HTMLMediaElement must be attached before load()!
• FlvPlayer.load() has been called, please call unload() first
• NativePlayer does't support flv MediaDataSource input!

AI-assisted analysis of bilibili/flv.js@42343088f2 (2026-09-01). Data as JSON: /api/errors/ec33ad209ab2e413. Report an issue: GitHub.