I’ll point to how many functional languages handle it. You create a type Maybe a, where a can be whatever type you wish. The maybe type can either be Just x or Nothing, where x is a value of type a (usually the result). You can’t access the x value through Maybe: if you want to get the value inside the Maybe, you’ll have to handle both a case where we have a value(Just x) and don’t(Nothing). Alternatively, you could just pass this value through, “assuming” you have a value throughout, and return the result in another Maybe, where you’ll either return the result through a Just or a Nothing. These are just some ways we can use Maybe types to completely replace nulls. The biggest benefit is that it forces you to handle the case where Maybe is Nothing: with null, it’s easy to forget. Even in languages like Zig, the Maybe type is present, just hiding under a different guise.

If this explanation didn’t really make sense, that’s fine, perhaps the Rust Book can explain it better. If you’re willing to get your hands dirty with a little bit of Rust, I find this guide to also be quite nice.

TLDR: The Maybe monad is a much better alternative to nulls.

One alternative are monadic types like result or maybe, that can contain either a value or an error/no value.

you could take a look at what Rust is doing with the Option enum. Superficially it looks similar to using null, but it actually accomplishes something very different.

A function that classically would return a value, say an int, but sometimes returns null instead, becomes a function that returns an Option. This forces explicit handling of the two cases, namely Some(value) or None. This way, it is next to impossible to try to do an operation on a value that does not exist.

This question illustrates the null problem succinctly.

json is one of the old things we now just have to deal with, since JS and by extension json implement a null value. And for parsing arbitrary json data, I currently don't have a good answer.

But when parsing a request payload, you usually know what properties to expect, and what types their values should be. Some keys are always present, for example UUIDs or other resource identifiers, and can therefore be directly parsed. But optional keys should be parsed differently, using Option Types. That way, you directly know what data type the field would have as well, if it were present. null in weakly-typed languages is especially bad in that regard, for example if you have something like this:

{
    "name": "Bob",
    "year": 1989
}

and both fields are nullable, you would expect them to be different types, but if they are both null, suddenly they're the same. The absence of a null type forces you to deal with optional values when parsing them, not when trying to do operations with them, which is the problem that null coalescing seeks to simplify.

I really like what Rust is doing in that regard, with the Option enum, and I know that functional programming languages like haskell have been doing it for a long time with their Maybe monad. I don't think functional programming is accessible enough to challenge most of the current paradigms, but this is definitely a thing we can learn from them.