Elysia.js

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State and Decorate ​

You can extend Elysia to fit your need. This is useful when you need to access extra values in a handler (e.g. a database connection).

In summary:

  • state: assign value to Context.store (a global state object of the Elysia instance)
  • decorate: assign value to Context

TIP

Context is a parameter in the callback of handler.

Example ​

typescript
app
    .state('version', 1)
    .decorate('getDate', () => Date.now())
    .get('/version', ({ 
        getDate, 
        store: { version } 
    }) => `${version} ${getDate()}`
)

app
    .state('version', 1)
    .decorate('getDate', () => Date.now())
    .get('/version', ({ 
        getDate, 
        store: { version } 
    }) => `${version} ${getDate()}`
)
  • version is registered using state, and accessible via Context.store.version.
  • getDate is registered using decorate, and accessible via Context.getDate.

TypeScript ​

You can type state and decorator explictly using TypeScript with as:

typescript
app
    // Will type version as `number | null`
    .state('version', 1 as number | null)
    .get('/version', ({ 
        store: { version } 
    }) => version

app
    // Will type version as `number | null`
    .state('version', 1 as number | null)
    .get('/version', ({ 
        store: { version } 
    }) => version

If explictly typed doesn't type null or undefined, make sure to set strict to true in tsconfig.json:

json
// tsconfig.json
{
  "compilerOptions": {
    "strict": true
  }
}

// tsconfig.json
{
  "compilerOptions": {
    "strict": true
  }
}