typescript-collections | A generically typed set of collections for use | Functional Programming library

TypeScript is just JavaScript on steroids. The only things is does is

1. Allows you to use types to make your code more predictable and find errors
2. Transforms some modern JS features like ?. and ??= operators into old JavaScript that any browser can understand, basically the same thing babel does

TypeScript doesn't provide any objects that don't exist in JavaScript. Map exists in JS - Map exists in TS, Set exists in JS - Set exists in TS, but there is no objects that TS has but JS doesn't. And it will probably never contain anything like that, because adding new functionality is not the goal of this project, it's goal is to add types to reduce errors when writing code. All TypeScript type annotations get deleted after compilation, because browsers can't understand them.

Well, to be fair, TypeScript can in fact add some code to your project, namely, regenerator runtime that lets you use things, such as async functions, for...of loops and more, but this is just to make modern JS features work in browsers that don't understand them, this is not to provide any kind of new functionality.

If you want a data structure, that doesn't exist in JS, such as LinkedList or Queue, you either have to write them and type definitions for them yourself or install a package, like mnemonist you mentioned. It's perfectly fine to do the latter and you can go with it. mnemonist even provides type definitions (.d.ts files), so you don't have to worry about them. If a package doesn't have type definitions included out of the box (like express) you will usually install type definitions from DefinitelyTyped (like @types/express). If type definitions haven't been written for the package you want, you will have to do it yourself. But this is not a problem in your case, you can just install mnemonist and go with it.