Web applications have become complex beasts and node.js allows to build programs that used to be other backend languages' turf. JavaScript developers now need to develop, as with any other programming language, custom data structures to solve particular problems when arrays and objects are simply not enough. The intention of this presentation is therefore to compile series of tips, tricks and use cases regarding the implementation of data structures in JavaScript and the challenges it poses. It is indeed tricky to ensure consistent performance in a high-level language with JIT and where engines like v8 apply a lot of optimization magic. One has to be able to evolve around those constraints. Examples will be taken from libraries such as graphology, sigma.js' newest version and finally mnemonist to demonstrate that 1. performant data structures can be designed for JavaScript using the language's capabilities and that 2. everyone can use them to solve problems more efficiently.