I notice you didn't mention any specifics, other than typescript can manipulate jsons - so can every other language in the world (and jsons are _horrible_ for data anyway)
Julia has one good library for this (JSON3.jl), but it really should be embedded in the language.
Furthermore, Julia has very nice support for multi-dimensional arrays, but it's built in support for dictionaries/hash maps isn't very good, and they might be more prevalent in many types of data processing (certainly in many "big data" types of workloads). There is another third party library for this (Dictionaries.jl) but once again, in practice, JavaScript and TypeScript not only much faster and more optimized for this, but also have better tooling available out of the box.
Again, not a knock on Julia at all, it's great for certain things, but it's important to understand where the ecosystem has gaps are and where things can be learned from other ecosystems.