I feel like I can somewhat relate, I've been adding flowtype [0] annotations to my JS code, which is transpiled with babel. However, since I'm using unsupported ES2015 features and experimental ES2016+ features, it fails to run over my code (which is completely understandable).
The workaround I've found is to use a plugin [1], which converts the type annotations into runtime checks. It's not perfect, but I've found it helps catch some bugs quickly. It's also really helpful for documentation purposes: you know that this function param takes a number param, if you're not passing in a number you've made a mistake. Also, having the inline type is nicer than having it in a jsdoc-style comment above.
I think there's diminishing returns as you add more annotations to your code and you make them stricter, but having basic sanity checks has been helpful in catching stupid mistakes quickly.
The workaround I've found is to use a plugin [1], which converts the type annotations into runtime checks. It's not perfect, but I've found it helps catch some bugs quickly. It's also really helpful for documentation purposes: you know that this function param takes a number param, if you're not passing in a number you've made a mistake. Also, having the inline type is nicer than having it in a jsdoc-style comment above.
I think there's diminishing returns as you add more annotations to your code and you make them stricter, but having basic sanity checks has been helpful in catching stupid mistakes quickly.
[0] http://flowtype.org/ [1] https://github.com/codemix/babel-plugin-typecheck