---
title: "script:updated Hook"
description: "Learn about the script:updated hook in Unhead that's triggered when a script instance is updated"
navigation:
  title: "script:updated"
internal: true
---

The `script:updated` hook is called when a script instance managed by Unhead is updated. This hook is specific to Unhead's script management features and provides a way to react to changes in script status, such as loading, execution, or errors.

## Hook Signature

```ts
export interface Hook {
  'script:updated': (ctx: { script: ScriptInstance<any> }) => void | Promise<void>
}
```

### Parameters

| Name | Type | Description |
|------|------|-------------|
| `ctx` | Object | Context object with script information |
| `ctx.script` | `ScriptInstance<any>` | The script instance that was updated |

### Returns

`void` or `Promise<void>`

## Usage Example

```ts
import { createHead } from '@unhead/dynamic-import'

const head = createHead({
  hooks: {
    'script:updated': (ctx) => {
      // Log script status changes
      const { script } = ctx
      console.log(`Script "${script.id}" updated, status: ${script.status}`)

      // React to specific script updates
      if (script.id === 'analytics' && script.status === 'loaded') {
        console.log('Analytics script has loaded successfully')
      }
    }
  }
})
```

## Use Cases

### Script Loading Monitoring

Track script loading status across your application:

```ts
import { defineHeadPlugin } from '@unhead/dynamic-import'

export const scriptMonitoringPlugin = defineHeadPlugin({
  hooks: {
    'script:updated': (ctx) => {
      const { script } = ctx

      // Log detailed script status updates
      switch (script.status) {
        case 'loading':
          console.log(`Script loading started: ${script.id}`)
          break
        case 'loaded':
          console.log(`Script loaded successfully: ${script.id}`)
          break
        case 'error':
          console.error(`Script failed to load: ${script.id}`, script.error)
          break
        case 'idle':
          console.log(`Script waiting: ${script.id}`)
          break
      }

      // Track loading times for performance monitoring
      if (script.status === 'loaded' && script.loadStart) {
        const loadTime = Date.now() - script.loadStart
        console.log(`Script "${script.id}" loaded in ${loadTime}ms`)

        // Report to analytics or performance monitoring
        if (window.performance && window.performance.mark) {
          window.performance.mark(`script-${script.id}-loaded`)
          window.performance.measure(
            `script-${script.id}-load-time`,
            `script-${script.id}-loading`,
            `script-${script.id}-loaded`
          )
        }
      }
    }
  }
})
```

### Dependency Management

Manage script dependencies and trigger actions when scripts load:

```ts
import { defineHeadPlugin } from '@unhead/dynamic-import'

export const scriptDependencyPlugin = defineHeadPlugin({
  hooks: {
    'script:updated': (ctx) => {
      const { script } = ctx

      // Track loaded scripts in a global registry
      if (!window.__LOADED_SCRIPTS) {
        window.__LOADED_SCRIPTS = new Set()
      }

      if (script.status === 'loaded') {
        // Add to loaded scripts registry
        window.__LOADED_SCRIPTS.add(script.id)

        // Check for dependency chains
        checkDependencies(script.id)
      }
    }
  }
})

// Helper function to check and execute dependent scripts
function checkDependencies(loadedScriptId) {
  // Define script dependencies (scripts that depend on others)
  const dependencyMap = {
    'maps-init': ['google-maps-api'],
    'analytics-enhanced': ['analytics-base'],
    'shop-components': ['vue', 'shopping-cart-api']
  }

  // Check if any scripts are waiting for this one
  Object.entries(dependencyMap).forEach(([scriptId, dependencies]) => {
    if (dependencies.includes(loadedScriptId)) {
      // Check if all dependencies for this script are now loaded
      const allDepsLoaded = dependencies.every(dep =>
        window.__LOADED_SCRIPTS.has(dep)
      )

      if (allDepsLoaded) {
        console.log(`All dependencies loaded for ${scriptId}, initializing...`)
        initScript(scriptId)
      }
    }
  })
}

// Helper function to initialize dependent scripts
function initScript(scriptId) {
  // This would handle the initialization of scripts that depend on others
  console.log(`Initializing dependent script: ${scriptId}`)

  // Your actual initialization logic would go here
  // For example, you might call a global function that was loaded
  if (scriptId === 'maps-init' && window.google && window.google.maps) {
    window.initGoogleMaps?.()
  }
}
```

### Error Recovery

Implement error recovery strategies for failed scripts:

```ts
import { defineHeadPlugin } from '@unhead/dynamic-import'

export const scriptErrorRecoveryPlugin = defineHeadPlugin({
  hooks: {
    'script:updated': (ctx) => {
      const { script } = ctx

      // Handle script loading errors
      if (script.status === 'error') {
        console.error(`Script "${script.id}" failed to load:`, script.error)

        // Track retry attempts
        script.retryCount = (script.retryCount || 0) + 1

        // Implement retry strategy with exponential backoff
        if (script.retryCount <= 3) {
          const backoffTime = 2 ** script.retryCount * 1000
          console.log(`Retrying script "${script.id}" in ${backoffTime}ms (attempt ${script.retryCount}/3)`)

          setTimeout(() => {
            // Reset status and try again
            script.status = 'idle'

            // Use a different CDN or fallback URL if available
            if (script.retryCount > 1 && script.fallbackSrc) {
              script.src = script.fallbackSrc
              console.log(`Using fallback source for "${script.id}": ${script.fallbackSrc}`)
            }

            // Trigger reload
            script.load()
          }, backoffTime)
        }
        else {
          // After max retries, log failure and try to recover app state
          console.error(`Script "${script.id}" failed after ${script.retryCount} retry attempts`)

          // Notify user if the script was critical
          if (script.critical) {
            showUserErrorNotification(script.id)
          }

          // Try to load from local fallback if available
          if (script.localFallback) {
            console.log(`Loading local fallback for "${script.id}"`)
            loadLocalFallback(script.id, script.localFallback)
          }
        }
      }
    }
  }
})

// Helper functions for error recovery
function showUserErrorNotification(scriptId) {
  console.log(`Showing error notification for script: ${scriptId}`)
  // Your notification logic
}

function loadLocalFallback(scriptId, fallbackPath) {
  console.log(`Loading local fallback for ${scriptId} from ${fallbackPath}`)
  // Your fallback loading logic
}
```