# Server Actions

[Server Actions](https://react.dev/reference/rsc/server-actions) are **asynchronous functions** that are executed on the server. Basically replace using api routes

* Defined with the React [`"use server"`](https://react.dev/reference/react/use-server) directive
* Can pass/use server
* errors caught by suspense/error boundary

```tsx
export default function Page() {
  // Server Action
  async function create() {
    'use server'
    // Mutate data
  }
 
  return '...'
}
```

Can separate in different files

app/actions.ts

```ts
'use server'
 
import { z } from 'zod'
 
const schema = z.object({
  email: z.string({
    invalid_type_error: 'Invalid Email',
  }),
})
 
export default async function createUser(formData: FormData) {
  const validatedFields = schema.safeParse({
    email: formData.get('email'),
  })
 
  // Return early if the form data is invalid
  if (!validatedFields.success) {
    return {
      errors: validatedFields.error.flatten().fieldErrors,
    }
  }
 
  // Mutate data
}
```

app/ui/button.tsx

```tsx
'use client'
 
import { useFormState } from 'react'
import { createUser } from '@/app/actions'
 
const initialState = {
  message: '',
}
 
export function Signup() {
  const [state, formAction] = useFormState(createUser, initialState)
 
  return (
    <form action={formAction}>
      <label htmlFor="email">Email</label>
      <input type="text" id="email" name="email" required />
      {/* ... */}
      <p aria-live="polite">{state?.message}</p>
      <button>Sign up</button>
    </form>
  )
}
```


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