Server Config - Wasp

import { CardLink } from "@site/src/components/CardLink"; import { ShowForTs, ShowForJs } from "@site/src/components/TsJsHelpers";

You can configure the behavior of the server via the server field of app spec:

import { app } from "@wasp.sh/spec"
import { myMiddlewareConfigFn, mySetupFunction } from "./src/myServerSetupCode" with { type: "ref" }

export default app({
  name: "MyApp",
  title: "My app",
  server: {
    setupFn: mySetupFunction,
    middlewareConfigFn: myMiddlewareConfigFn,
  },
  // ...
})

Setup Function

<ShowForTs> `setupFn` declares a Typescript function that will be executed on server start. </ShowForTs> <ShowForJs> `setupFn` declares a Javascript function that will be executed on server start. </ShowForJs>

Adding a Custom Route

As an example, adding a custom route would look something like:

<Tabs groupId="js-ts"> <TabItem value="js" label="JavaScript"> ```js title="src/myServerSetupCode.js" export const mySetupFunction = async ({ app }) => { addCustomRoute(app) }

function addCustomRoute(app) {
  app.get("/customRoute", (_req, res) => {
    res.send("I am a custom route")
  })
}
```

</TabItem> <TabItem value="ts" label="TypeScript"> ```ts title="src/myServerSetupCode.ts" import { ServerSetupFn } from "wasp/server" import { Application } from "express"

export const mySetupFunction: ServerSetupFn = async ({ app }) => {
  addCustomRoute(app)
}

function addCustomRoute(app: Application) {
  app.get("/customRoute", (_req, res) => {
    res.send("I am a custom route")
  })
}
```

</TabItem> </Tabs>

Storing Some Values for Later Use

In case you want to store some values for later use, or to be accessed by the Operations you do that in the setupFn function.

Dummy example of such function and its usage:

<Tabs groupId="js-ts"> <TabItem value="js" label="JavaScript"> ```js title="src/myServerSetupCode.js" let someResource = undefined

export const mySetupFunction = async () => {
  // Let's pretend functions setUpSomeResource and startSomeCronJob
  // are implemented below or imported from another file.
  someResource = await setUpSomeResource()
  startSomeCronJob()
}

export const getSomeResource = () => someResource
```

```js title="src/queries.js"
import { getSomeResource } from "./myServerSetupCode.js"

...

export const someQuery = async (args, context) => {
  const someResource = getSomeResource()
  return queryDataFromSomeResource(args, someResource)
}
```

</TabItem> <TabItem value="ts" label="TypeScript"> ```ts title="src/myServerSetupCode.ts" import { type ServerSetupFn } from "wasp/server"

let someResource = undefined

export const mySetupFunction: ServerSetupFn = async () => {
  // Let's pretend functions setUpSomeResource and startSomeCronJob
  // are implemented below or imported from another file.
  someResource = await setUpSomeResource()
  startSomeCronJob()  
}

export const getSomeResource = () => someResource
```

```ts title="src/queries.ts"
import { type SomeQuery } from "wasp/server/operations"
import { getSomeResource } from "./myServerSetupCode.js"

...

export const someQuery: SomeQuery<...> = async (args, context) => {
  const someResource = getSomeResource()
  return queryDataFromSomeResource(args, someResource)
}
```

</TabItem> </Tabs>

:::note The recommended way is to put the variable in the same module where you defined the setup function and then expose additional functions for reading those values, which you can then import directly from Operations and use.

This effectively turns your module into a singleton whose construction is performed on server start. :::

For the full description of the setupFn field, check the Server API Reference.

Middleware Config Function

You can configure the global middleware via the middlewareConfigFn. This will modify the middleware stack for all operations and APIs.

Read more in the configuring middleware section.

API Reference