TypeError: undefined does not have a method named "concat"

I have started having problems with a multipage app I am working on. The app has started hanging on 2 of the 5 pages. There are no error messages in the terminal. I haven’t managed to isolate the problem to any specific callbacks.

I know very little about javascript, but these are the errors that appear in the Firefox console:

Unhandled promise rejection TypeError: undefined does not have a method named “concat”
Stack trace:
_ bundle.js:19:22669_

And these are the errors in the Chrome console:

Uncaught (in promise) TypeError: undefined does not have a method named “concat”
_ at bundle.js:2_
_ at e (bundle.js:1)_
_ at bundle.js:1_
_ at Array.map ()_
_ at l (bundle.js:1)_
_ at bundle.js:2_
_ at Array.forEach ()_
_ at bundle.js:2_

Any assistance would be greatly appreciated.

1 Like

I rolled back dash-renderer to version 0.11.0 and the errors went away. Unfortunately I use tabs throughout the app, so I can’t use that version.

@chriddyp perhaps it is a similar issue to this: