[ifuller1]

I'm not sure that embracing a languages dynamic nature should get in the way of leveraging libraries to write more readable code. One advantage of using a standard approach (be it a third party library, or something bespoke) is that you could enable / disable the 'type checking' depending on the build environment. I wouldn't be surprised if your existing toolchain isn't already bringing some static inference to your development - are you using jsdoc and an IDE with autocomplete, for example?

Trusting you find Dart, Typescript, et al agreeable you have to concede that some people are working with legacy code and can only make iterative changes to their codebase?