What causes "Tried add listener but no event specified." in quasarframework/quasar?

Pass a non-empty string as the first argument to on().

Tried add listener but no event specified.

Error message

Tried add listener but no event specified.

What it means

BexBridge.on(event, callback) was called with an empty/undefined/falsy event name. The bridge warns and skips registering the listener instead of throwing.

Source

Thrown at app-vite/exports/bex/private/bex-bridge.js:263

        'Tried to disconnect from the background script but the port was not connected'
      )
    }

    this.portMap.background.disconnect()
    delete this.portMap.background
    this.isConnected = false
    // an explicit disconnect also opts out of the auto-reconnect behavior
    this.#wasConnected = false
    return Promise.resolve()
  }

  /**
   * @param {string} event
   * @param {(message: Message) => void} callback
   */
  on(event, callback) {
    if (!event) {
      this.warn('Tried add listener but no event specified.')
      return
    }

    if (typeof callback !== 'function') {
      this.warn('Tried add listener but no valid callback function specified.')
      return
    }

    const target = (this.listeners[event] ||= [])
    target.push({ type: 'on', callback })
    this.log(`Added a listener for event: "${event}".`)
  }

  /**
   * @param {string} event
   * @param {(message: Message) => void} callback
   */
  once(event, callback) {

View on GitHub (pinned to 4841521b5f)

Solutions

Pass a non-empty string as the first argument to on().
Check that the event-name constant is actually imported/defined (undefined imports yield falsy names).
Log the event argument before calling to confirm its value.

Example fix

// before
bridge.on(EVENT_NAME, handler) // EVENT_NAME undefined
// after
if (typeof EVENT_NAME !== 'string' || EVENT_NAME.length === 0) {
  throw new Error('EVENT_NAME must be a non-empty string')
}
bridge.on(EVENT_NAME, handler)

Defensive patterns

Strategy: validation

Validate before calling

if (typeof event !== 'string' || event.length === 0) {
  throw new TypeError('bridge.on requires a non-empty event name')
}
bridge.on(event, callback)

Type guard

const isValidEventName = (e) => typeof e === 'string' && e.trim().length > 0

Prevention

Define event names as exported constants.
Validate dynamic event names before subscribing.
Check for undefined imports from circular dependencies.

When it happens

Trigger: bridge.on(undefined, fn), bridge.on('', fn), or passing a variable that is not yet assigned as the event name.

Common situations: Event name read from config/env that is missing; typo where the event constant is undefined due to a circular import or wrong import path.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of quasarframework/quasar@4841521b5f (2026-08-30). Data as JSON: /api/errors/d9736d2556ad8634. Report an issue: GitHub.