# Elm exceptions when loading in hidden iframe in Firefox, sometimes
**URL:** https://discourse.elm-lang.org/t/elm-exceptions-when-loading-in-hidden-iframe-in-firefox-sometimes/2363
**Category:** Learn
**Created:** [October 30, 2018, 4:35pm UTC](https://discourse.elm-lang.org/t/elm-exceptions-when-loading-in-hidden-iframe-in-firefox-sometimes/2363 "2018-10-30T16:35:35Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@wondible](https://discourse.elm-lang.org/u/wondible)
#### Post date: [October 30, 2018, 4:35pm UTC](https://discourse.elm-lang.org/t/elm-exceptions-when-loading-in-hidden-iframe-in-firefox-sometimes/2363/1 "2018-10-30T16:35:35Z")
I’m sometimes getting elm exceptions when running under the [Twitch Extension Developer Rig](https://github.com/twitchdev/developer-rig) The rig runs a page in multiple levels of iframes, one of which is hidden and then shown shortly afterwards. (In Firefox I’ve had issues with canvas tags created while iframe is hidden being invalid.)
Every once and a while, I get a stream of Elm exceptions `TypeError: domNode is undefined`, `TypeError: undefined has no properties` from
`var childNodes = domNode.childNodes;`
in `_VirtualDom_addDomNodesHelp`
It appears to be from a recursive call from the same function
`i = _VirtualDom_addDomNodesHelp(childNodes[j], vKid, patches, i, low, nextLow, eventNode);`
where childNodes has 3 elements, and the j iterator is 3 or 4 when I’ve inspected.
Has anybody seen a problem like this before?
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### Author:  [@system](https://discourse.elm-lang.org/u/system)
#### Post date: [November 9, 2018, 4:35pm UTC](https://discourse.elm-lang.org/t/elm-exceptions-when-loading-in-hidden-iframe-in-firefox-sometimes/2363/2 "2018-11-09T16:35:35Z")
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