As your typical type hater, my preferred argument is: yes, static typing prevents a certain class of bugs from happening; no, this class of bugs is not nearly as relevant as type lovers seem to be claiming. By an order of magnitude if not more.
Source: 6 years of being a core developer of a front end framework consisting of 1,500,000 lines of ES5 JavaScript and SASS.
If your usual workflow is to defer all of the typing information to the IDE, rather than keeping it in your head. Then the second you can't access that information at a whim, you're fucked. It's like how I can't navigate around my city without Google Maps, because I've never had much of a reason to.
That metaphor works well, because Google Maps is probably a net positive. It's just that if I go around waving my phone in the face of a 60 year old cab driver that knows where everything is, going "I can't understand how you think you can get around without GPS, you're making loads of mistakes without realising it", I'm going to look like a fucking moron.
This is just not at all how it works in practice. You still keep it all in your head, but the compiler errors protect you from small mistakes.
No matter how great of a programmer you are, you will make transcription errors with the things you have in your head. This is literally exactly the type of "I don't make mistakes" nonsense that I said was common, and a bunch of other people said was extreme and a strawman.
There's more ways than type hints to fail fast. I'm not saying me and all the other JS devs don't make mistakes. I'm saying the mistakes we make are ones that we catch in 5 seconds because the modern web dev environment is set up to facilitate that. Typescript devs make additional mistakes on top of that beacuse they have tools that catch those mistakes quickly too. We don't, so we get conditioned to program in a way to prioritise not making those mistakes (possibly at the expense of other mistakes becoming more common).
The point is that someone with years of JS experience is going to be more productive with JS, and someone with years of TS experience is going to be more productive with TS. I'm not saying Typescript sucks, just that the cost side of it's cost/benefit equation isn't the same for every dev, whereas your shit argument assumes that it is because you only base it on your own experience.
It is interesting how "protecting from small mistakes" is touted as "solving our API woes", innit?
At some point it is liberating to admit that static vs dynamic is a matter of personal preference and nothing more. If I like it, I will find a thousand reasons to justify it, and vice versa.
I just wish everybody would be open about it: I like "type safety" and the warm fuzzy feeling it gives me, and nothing you unwashed heathens can say about tight coupling, increased incidental complexity, over-engineered APIs and productivity loss can sway my opinion! Why, my productivity is _increased_ with static typing, because I make up for hours of bikeshedding about which type better conveys the underlying intent with writing less null checks and unit tests! Take that, type haters!
Meh, wishful thinking.
This rings true, especially given that in my experience, most of the static typed people either never worked with dynamic languages at all, or converted from dynamic to static. Most of the dynamic minded people I know actually converted _from_ static typing after doing that for years (myself included).
The calculus is pretty simple IMO: if one has mental discipline to work with a dynamic weakly typed language, not having to mess with types and compilers is downright liberating: ye godz, just gimme that data! On the other hand the people who never experienced conditions leading to developing said mental discipline tend to abhor the idea of not having the "type safety" (cute marketing, that). Hence the chasm between Lisp crowd and Haskell mob, with JavaScript being the perpetual battleground somewhere in between.
I used to do a lot of things on it, including _very_ deep refactorings with sweeping changes across the codebase. The secret sauce is focus on automated testing: when I left the company, we had ~70,000 test specs for the framework, and the test suite was executed on each commit to every PR pushed to Github. Depending on framework version (there were several in flight), and browser matrix (15+ supported browsers), each test run yielded 500,000-700,000 spec results (and finished in under 20 minutes).
There was a lot of custom tooling around this, of course. Including a test runner that I got open sourced right before leaving the company: https://github.com/sencha/jazzman. Sadly it looks like there were no new commits since I left; I hoped to pick it up later but so far I haven't encountered the need to run significantly sized test suites in massively parallel fashion. Nobody writes that many tests. :)
EDIT: I almost forgot that as a condition for open-sourcing the test runner they made me write a blog post about it: https://www.sencha.com/blog/ext-js-testing-story-under-the-h... :)
It is that big because it implements a lot of things that other frameworks don't even try to try thinking about, things mostly used to build very boring line of business applications (think thousands of forms, huge grids, reports with charts, etc). Applications built with Ext JS can easily dwarf the framework itself; the biggest I've seen personally was ~30 mb of minified ES5 JavaScript.
...and it worked in IE8, BTW. :)