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TypeScript

Example: TypeScript and Schema

Convex provides end-to-end type support when Convex functions are written in TypeScript.

You can gradually add TypeScript to a Convex project: the following steps provide progressively better type support. For the best support you'll want to complete them all.

Writing Convex functions in TypeScript​

The first step to improving type support in a Convex project is to writing your Convex functions in TypeScript. TypeScript inference is so good that the difference between writing a Convex function in JavaScript and TypeScript may be very small! Start by renaming the convex module from e.g. addChannel.js to addChannel.ts and add annotations for function parameters.

import { mutation } from "./_generated/server";

export default mutation(
  // The only change required to convert this function to
  // TypeScript is annotating the type of a parameter `name`
  async ({ db }, name: string) => {
    return db.insert("channels", { name });
  }
);

If TypeScript is installed in your project npx convex dev and npx convex deploy will typecheck Convex functions before sending code to the Convex backend.

Convex functions are typechecked with the tsconfig.json in the Convex folder: you can modify some parts of this file to change typechecking settings, or delete this file to disable this typecheck.

You'll find most database methods have a return type of Promise<any> until you add a schema.

Adding a schema​

Once you define a schema the type signature of database methods will be known. You'll also be able to use types imported from convex/_generated/dataModel in both Convex functions and application code.

The types of documents in tables can be described using Document from the generated data model and references to documents can be described with parametrized Document IDs.

import { Document, Id } from "../convex/_generated/dataModel";

function Channel(props: { channelId: Id<"channels"> }) { ... }
function MessagesView(props: { message: Document<"messages"> }) { ... }

Writing frontend code in TypeScript​

Invocations of useQuery and useMutation the signatures of their corresponding Convex functions. For end to end type safety, install and configure TypeScript so you can write your React components in .tsx files instead of .jsx files.

Convex works best with TypeScript version 4.8.4 or newer.