Please post to openHAB 4.0 SNAPSHOT discussion where the 4.0 SNAPSHOT problems are discussed.
Note that timerDuration in this case is a String. The .state is always a String. You might need to parse it to a Number first.
But in any case, this is 100% implemented in the joda-js library so any issue would need to be filed and corrected there. It’s not an OH problem.
How is the Thing defined? In a text file or through the UI?
What use case would have you changing the label of a Thing?
Note, this code is not correct (missing a closing ’ on the first line).
Which version of openhab-js are you using? The metadata was completely reworked in the latest release.
Show the full config from the “Code” tab.
You are testing the 4.0 SNAPSHOT. Tons of breaking changes are being introduced with almost every build. Welcome to the bleeding edge.