> ## Documentation Index > Fetch the complete documentation index at: https://docs.ad-unblock.com/llms.txt > Use this file to discover all available pages before exploring further. # Express > Express middleware for script loading and injection with TypeScript support A powerful Express middleware for server-side script loading and injection. Load external scripts from remote JSON endpoints with caching, security, and flexible integration options. Built with TypeScript for full type safety. ## Installation ```bash theme={null} npm install @adunblock/server-tag-express ``` Every rendered ``) .join("\n"); res.send(`${scriptTags}...`); }); ``` ## Configuration Options | Option | Type | Default | Description | | ------------------ | ------------------ | --------------- | --------------------------------------- | | `remoteUrl` | `string` | **Required** | URL to fetch script configuration from | | `cacheInterval` | `number` | `300` | Cache duration in seconds | | `injectIntoHtml` | `boolean` | `true` | Auto-inject scripts into HTML responses | | `injectPosition` | `string` | `''` | Where to inject scripts in HTML | | `scriptAttributes` | `ScriptAttributes` | `{async: true}` | Additional attributes for script tags | | `onError` | `function` | `undefined` | Custom error handler function | | `shouldInject` | `function` | `() => true` | Conditional injection logic | ## Advanced Configuration ```typescript theme={null} import type { ServerTagMiddlewareOptions } from "@adunblock/server-tag-express"; const config: ServerTagMiddlewareOptions = { remoteUrl: "https://public.adunblocker.com/api/vendor_scripts", cacheInterval: 600, // 10 minutes injectIntoHtml: true, injectPosition: "", scriptAttributes: { defer: true, "data-source": "server-tag", }, shouldInject: (req, res) => { // Don't inject scripts on API routes return !req.path.startsWith("/api/"); }, onError: (error, req, res) => { console.error("ServerTag error:", error.message); // Optional: send error to monitoring service }, }; app.use(serverTagMiddleware(config)); ``` ## Route-Specific Configuration Apply ServerTag to specific routes with different configurations: ```typescript theme={null} // Global middleware app.use( serverTagMiddleware({ remoteUrl: "https://public.adunblocker.com/api/vendor_scripts", }) ); // Route-specific middleware app.get( "/special", serverTagMiddleware({ remoteUrl: "https://public.adunblocker.com/api/vendor_scripts", cacheInterval: 60, // 1 minute cache scriptAttributes: { defer: true }, }), (req, res) => { res.render("special-page"); } ); ``` ## API Reference ### `serverTagMiddleware(options)` Main middleware function that adds ServerTag functionality to Express apps. **Parameters:** * `options` (ServerTagMiddlewareOptions): Configuration options **Returns:** Express middleware function ### `injectScripts(html, scripts, attributes, position)` Helper function to manually inject scripts into HTML strings. **Parameters:** * `html` (string): HTML string to modify * `scripts` (string\[]): Array of script URLs * `attributes` (ScriptAttributes): Script tag attributes * `position` (string): Where to inject (default: `''`) **Returns:** Modified HTML string ### Type Definitions ```typescript theme={null} interface ServerTagConfig { cacheInterval?: number; timeout?: number; retries?: number; retryDelay?: number; } interface ScriptAttributes { async?: boolean; defer?: boolean; type?: string; [key: string]: string | boolean | number | undefined; } interface ServerTagMiddlewareOptions extends ServerTagConfig { remoteUrl: string; injectIntoHtml?: boolean; injectPosition?: string; scriptAttributes?: ScriptAttributes; onError?: (error: Error, req: Request, res: Response) => void; shouldInject?: (req: Request, res: Response) => boolean; } ``` ## Error Handling ServerTag includes robust error handling with custom error types: ```typescript theme={null} import { ServerTagError, NetworkError, ValidationError, TimeoutError, } from "@adunblock/server-tag-express"; app.use( serverTagMiddleware({ remoteUrl: "https://public.adunblocker.com/api/vendor_scripts", onError: (error, req, res) => { if (error instanceof NetworkError) { console.error("Network error:", error.message); } else if (error instanceof ValidationError) { console.error("Validation error:", error.message); } else if (error instanceof TimeoutError) { console.error("Timeout error:", error.message); } // Scripts will be empty array on error console.log("Scripts loaded:", res.locals.serverTagScripts?.length || 0); }, }) ); ``` ## Browser Compatibility ServerTag works with all browsers supported by the generated script tags. The middleware itself runs on Node.js 16+.