1. Mozilla
  2. Add-ons
  3. Browser extensions
  4. JavaScript APIs
  5. proxy
  6. proxy.onError

proxy.onError

Fired when there is an error evaluating the PAC file or the onRequest listener.

The error can be triggered by throwing or returning an invalid value in the proxy.onRequest event handler.

Syntax

js
browser.proxy.onError.addListener(listener)
browser.proxy.onError.removeListener(listener)
browser.proxy.onError.hasListener(listener)

Events have three functions:

addListener(listener)

Adds a listener to this event.

removeListener(listener)

Stop listening to this event. The listener argument is the listener to remove.

hasListener(listener)

Check whether listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

listener

The function called when this event occurs. The function is passed this argument:

newState

Object. An Error object representing the error.

Example extensions

Browser compatibility

Chrome
Edge
Firefox
Opera
Safari
Firefox for Android
Safari on iOS
onError
Chrome – No support
Chrome
footnote No support
Edge – No support
Edge
footnote No support
Firefox – No support
Firefox 55 – 70 (Release date: 2017-08-08)
altname
footnote Removed in 71 and later
altname Alternate name: onProxyError
Firefox – Full support
Firefox 60 (Release date: 2018-05-09)
footnote Full support
Opera – No support
Opera
footnote No support
Safari – No support
Safari
footnote No support
Firefox for Android – Full support
Firefox for Android 55 (Release date: 2017-08-08)
altname
altname Alternate name: onProxyError
Firefox for Android – Full support
Firefox for Android 60 (Release date: 2018-05-09)
footnote Full support
Safari on iOS – No support
Safari on iOS
footnote No support

Tip: you can click/tap on a cell for more information.

Full support
No support
Uses a non-standard name
Has more compatibility info.

This page was last modified on by MDN contributors.

Visit Mozilla Corporation’s not-for-profit parent, the Mozilla Foundation.
Portions of this content are ©1998–2026 by individual mozilla.org contributors. Content available under a Creative Commons license.