I was unsure if this comment was sarcasm so I tried and concatenating a function and a string in JS actually results in the source of the function being concatenated with the string.

<rant> This whole "wow I thought implicit type coercion in JS was a joke" style comment got old 10 years ago. If you look at where JS came from (the 90s browser) and what it tried to do there then you should be left with few surprises looking it JS code snippets. If you don't understand what a language was designed for and how it evolved how can you be surprised at the results of code snippets? Because it's not the same as every other language? What would the point of the new language be then?</rant>

It’s not that the language is different, it’s that the default is stupid. It’s much more likely that if I’m trying to concatenate a string and a function, I’ve mistyped something, not that I want the source code of the function.

You can always include some additional function which takes a function as an argument and prints the source code as a string for the 4 people in the world who rely on function to string coercion, why is it a default behavior with no visibility?

I get it, JS is different from C or C++ and every other language but we call out poor design decisions by comparing them to expectations fostered by other languages

Again how can you say it's an outrageous default if all you reference is what you think it should have done from a generic language PoV not looking to understand why it does it that way?

Javascript came in as a scripting language for working with the untyped string content of a browser so you get dynamic duck typing where it tries to make the types work (generally towards string since that's what the browser had) instead of having the scripter trying to make some simple web content dynamic do more type checks than actual code. In JS functions are just objects (like most everything) and objects. Combine the above so when you say object + "foo" it coerces object to string and it shouldn't seem outrageous just not what you're used to.

Now a fair question would be "Why doesn't TS consider this an error out of the box".

Also for those annoyed by this in places JS wasn't originally designed to go (heavy app logic, server backends, desktop applications) you might want to look at the no-implicit-coercion rule in ESLint or similar.

I have been coding TypeScript for the last 2 years, non-stop, which also shielded me from the surprise of the function's body getting stringified.

It's relatable. Most developers did not grow up with the knowledge of JS language's Design principles, which is not something I would criticize anyone for.