Cocos Creator Web Global Error Handling: error, unhandledrejection and Resource Failures

After a game is released, bugs can be invisible until a player reports them—and even then, the report may not reveal where the problem occurred. I added global error listeners and sent diagnostics to a server, which also uncovered errors that players never reported.

Register Global Error and Promise Rejection Listeners

Different error types require different listeners. This implementation applies only to web builds; native builds will not report through these browser APIs.

window.onerror = (message, source, lineno, colno, error) => {
    if (lineno != lineno1 && colno1 != lineno && message != message1) {
        HttpReq.Ins.reqDotting(error, {
            type: `5`,
            content: `Global error: source ${source}, line ${lineno}, column ${colno}`,
            additional: `Error object: ${error}`
        });
    }
    lineno1 = lineno;
    colno1 = colno;
    message1 = message;
    return true;
};

window.addEventListener('unhandledrejection', (event) => {
    const errorInfo = { message: '', stack: '' };

    if (event.reason instanceof Error) {
        errorInfo.message = event.reason.message;
        errorInfo.stack = event.reason.stack;
    } else {
        errorInfo.message = event.reason.toString();
    }

    HttpReq.Ins.reqDotting(ClientDottingName.error, {
        type: `3`,
        content: `Unhandled Promise rejection`,
        additional: JSON.stringify(errorInfo)
    });
});

window.addEventListener('error', (event) => {
    const target = event.target as HTMLElement;
    if (target && (target.tagName === 'IMG' || target.tagName === 'SCRIPT' || target.tagName === 'LINK')) {
        HttpReq.Ins.reqDotting(error, {
            type: `4`,
            content: `Resource failed to load`,
            additional: `${target.getAttribute('src') || target.getAttribute('href')}`
        });
    }
}, true);

Replace the reporting calls with your own API. Also rate-limit and deduplicate reports: a global error can fire repeatedly and overwhelm both the game and the server. This example avoids reporting the same line, column, and message repeatedly.

To map a production stack trace back to source, see Mapping Cocos Creator Production Errors Back to Source Code.