To clarify the term ‘nesting’, I simply mean that interface A contains a property, which is described by interface B. The babel typescript preset does not work exactly as we want it to. A Type Declaration or Type Definition file is a TypeScript file but with .d.ts filename extension. TypeScript 2.4 added support for dynamic import() expressions, which allow you to asynchronously load and execute ECMAScript modules on demand.. At the time of writing in January 2018, the official TC39 proposal for dynamic import() expressions is at stage 3 of the TC39 process and has been for a while, which … There are more things to export and import, such as interfaces, types, namespaces, and enums. Dynamic import() Expressions in TypeScript January 14, 2018. Within the src/models directory, create a sub-directory called items. Because with the Babel variant there are two kind of important features missing (type imports and interface exports / re-exports) - at least that we know of now. extending an incomplete typescript sdk definition There are times when the TypeScript SDK does not include definitions for a property or function already supported by some browsers. Within this directory we’ll add a new TypeScript file called IItem.ts. The export of those interfaces allows us to import it just like we would do for the BarChart, itself. This means you can: import/require files with extension .ts/.tsx! For types that I frequently reuse I have a top level types.ts file, so stuff like a User interface would exist there. It kinda depends. ; Multiple tsconfigs support just like normal. I am hoping to convince you to do your best to avoid this practice where you can. So what so special about these Type Declaration files and how they are different from normal… Consider using a class instead of an interface.. If you’re curious what types can be used in an interface, you can checkout my article on an Overview of TypeScript Types. Nesting TypeScript interfaces can be a great way of keeping your code neat and clean. The practice of using classes as interfaces in TypeScript is most commonly promoted in the Angular style guide, which says (emphasis mine):. Note: we’ll be following a naming convention for TypeScript files that represents the interface and/or data models contained within the file. Typescript interfaces will disappear at compilation anyway - I just don't get why we could import an interface from a .ts file to another one, but not to a .svelte document's typescript