The JavaScript portion of the application presents the transactions data to the user and allows them to easily add, edit, and remove transactions. The application is split across several files to simplify the development process and uses the libraries described in the JavaScript libraries used section of this chapter. In this section, we will build the application step by step, starting with the API and global state interaction layer. We'll write functions to instantiate and interact with our Wasm module and review the Vue components required to build the user interface.