Cloudflare Docs
Workers
Cloudflare Docs
Workers
Search icon (depiction of a magnifying glass)
GitHub icon
Visit Workers on GitHub
Set theme to dark (⇧+D)

addEventListener

Background

The addEventListener function defines triggers for a Worker script to execute. There are currently two types of event listeners - "fetch" listeners which are sent a FetchEvent and "scheduled" listeners which are sent a ScheduledEvent .

Syntax

  • addEventListener(type, listener) void

    • If multiple "fetch" listeners are registered, when one does not call event.respondWith() , the runtime delivers the event to the next registered listener.
    • A "fetch" listener and a "scheduled" listener can be registered in the same script.
    • A script can have only one "scheduled" listener.

Properties

  • type string

    • The only types supported are "fetch" and "scheduled".

  • listener function

    • The function to handle incoming events to the Worker script. The listener is passed a single argument:

    • event FetchEvent or ScheduledEvent

Examples

Fetch Listener 

addEventListener('fetch', event => {
  event.respondWith(new Response('Hello world'));
});

Scheduled Listener 

addEventListener('scheduled', event => {
  event.waitUntil(handleScheduled(event));
});