octobercms/october · error · Error

Invalid handler name. The correct handler name format is: "o

Error message

Invalid handler name. The correct handler name format is: "onEvent".

What it means

Error "Invalid handler name. The correct handler name format is: "onEvent"." thrown in octobercms/october.

Source

Thrown at modules/backend/vuecomponents/uploader/assets/js/queue.js:5

import PQueue from 'p-queue';

function uploadAjaxRequest(handler, requestData, onProgress, abortSignal) {
    if (!handler.match(/^(?:\w+\:{2})?on*/) && handler !== 'mediamanager') {
        throw new Error('Invalid handler name. The correct handler name format is: "onEvent".');
    }

    return new Promise((resolve, reject) => {
        if (abortSignal?.aborted) {
            return resolve();
        }

        const xhr = new XMLHttpRequest();
        xhr.open('POST', window.location.href);

        const token = getToken();
        if (token) {
            xhr.setRequestHeader('X-CSRF-TOKEN', token);
        }

        if (handler !== 'mediamanager') {
            xhr.setRequestHeader('X-AJAX-HANDLER', handler);
            xhr.setRequestHeader('X-Requested-With', 'XMLHttpRequest');

View on GitHub (pinned to b608633a7e)

When it happens

Trigger: Thrown at modules/backend/vuecomponents/uploader/assets/js/queue.js:5 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of octobercms/october@b608633a7e (2026-08-21). Data as JSON: /api/errors/1ee6bc18574a0ec0. Report an issue: GitHub.