Today I woke up with a client kind of panicking that their app wasn't working anymore. Had been working absolutely fine for 3 months now and today all of a sudden things went down in a bit of a train wreck.
They sent a pic of the error -- "moment is not a constructor".
Initially I was lost, but naturally I quickly realized that it was referring to momentjs.
I had to log in, check the code and simply change
new moment().format()
to
moment().format()
Probably one of the quickest debugs I've ever made.
And beyond trying to point fingers and know if it was my fault because not using moment properly or not, the fact that this just appeared today is annoying.
Plus this meant that I had to edit the app, naturally triggering an editor charge within the billing cycle.
So we're just paying now to edit one word from the code. I don't think it's fair.
I don't know if you have changed the way that the code is interpreted that lead to the error or the implementation of momentjs, but clearly something changed as all this was working absolutely fine since March 2025, now being July.
Don't want this to be a rant but obviously not very happy with things randomly popping up.
found this a bit interesting, so I had to so some searching and thought I'd share. technically, in javascript using new moment(), should work? However, with TypeScript I think this depends on how it's imported import * as moment from 'moment' (namespace import)
vs import moment from 'moment'; or import moment = require('moment'); (class/function import)
and TypeScript vs JavaScript
The moment library itself exports a function, not a class. I know javascript (including JavaScript files checked with TypeScript) lets you call new with a function, but I think TypeScript files require functions to have a construct signature indicating the function can be called with new. The library is now a legacy project and is in maintenance mode.... it's not deprecated, but there won't ever be any new breaking changes. At best, it gets security updates, so we can pretty much rule out the library as the reason for this change.
so I think the options for what happened are:
Retool made an update to ES6 from ES5
Retool is doing a full conversion to TypeScript and they found some .jsx files they forgot to change to .tsx and pushed an update to fix it
TypeScript pushed an update
imo, it's more likely TypeScript had an update as the 2 Retool options are results from full codebase conversion/changes - which are costly, usually avoided unless newer language features are needed, often have workarounds devs would rather use unless annoyed or yelled at.... but I mean, I'm probably a little biased here
I'm unfortunately not that technical between JS and TS so thanks for the knowledge
What is bizarre to me is that this had been working for 3 months straight.
I had changed from new Date() to use moment as I'm in Australia and dealing with Date had become a bit of a nightmare when trying to format things correctly for some uses.
I might have left the "new" there from when I changed it to moment(), but the annoying bit is that as I say this went unnoticed for months. It was working fine.
So something must have changed for this to manifest as a bug.
TypeScript had allowed new being called on functions for, as far as I can tell, 1 very specific use case involving backwards compatibility with pre-ES5 and older browsers... they even had to add command line flags just so older projects with certain configs could force the build to work and TS isn't really known for making 'exceptions to the rule' as it kinda goes against their whole 'strongly-typed' thing they got going on: new should expect a class or constructor function, but for momentjs, it gets a normal function...
This confuses TS when it does its type checking and sees new moment(), since normal functions don't have a constructor or a construct signature like classes and constructor functions respectively (here's your error "moment is not a constructor") it results in the type evaluation defaulting to new [any] and now we have a double conundrum where not only does TS all but disallows the any type but, also the any type still isn't a constructable entity (unless you set noImplicitAny: false, this is another spot they had to make an exception to the rule).
hmmm, I just realized a couple things. 1) Retool may have updated their tsconfg file causing your problem and 2) I probably should ask a couple questions
Do you know what device and browser (and possibly browser version) your client was using?
Was the app working for you or anyone else and just not that 1 client?
I'm pretty sure you're spot on with your #1 realization.
We also had to do a quick pass yesterday of our date formatted tables because some of our editors were using the new keyword when processing their data. Luckily there isn't much to do once the bit has been identified, but we are basically on monitor mode for any stragglers.
Yeah they're just using either Chrome or Edge on Win11.
And no, just them as it is an internal tool. They are the sole users of this. So no one else on the app at the same time.
I have noticed that sometimes things tend to get touchy with symbols so I asked if they were entering ", ' ,&,# or any symbol that sometimes they did break things while building and testing. The answer was no.
I asked them to restart the whole thing (the basic L1 starting point) and it was the same. So definitely no weird caching errors or browser funkiness.
When I logged in I tried to use it (macOS, Firefox) and still gave me the error.
Definitely something changed on the backend, perhaps as you say moving ES5 to ES6 could be one. I really don't know as I'm essentially a beginner still with JS.
It would've been great from the Retool team sending a few warnings or heads up note to people saying that an upgrade or migration was about to take place with the chance of breaking a few things.
Mostly to give a bit of credit if edits would be needed because of it. I am very aware that code is always changing, but it's never fun to get messages at 5:30AM saying things are not working.
They could start pushing changes every month, forcing people to edit apps every month, leading to a forceful subscription/charge. (That wouldn't to well)
