In React Router, a function that handles form submissions and data mutations on the server side.
In React Router, an action is a Function that handles form submissions (POST, PUT, DELETE requests). When a user submits a Form, the action receives the formData and processes it — updating the Database, creating resources, or deleting items.
Actions are tied to routes — each route can have its own action. The action extracts data using request.formData(), runs Validation checks, sends it to your API (like Supabase), and returns a response. If it succeeds, the action typically calls Redirect to navigate to the new resource. If it fails, it returns an error object that useActionData displays to the user.
Server-side Middleware can validate requests before actions run. Actions separate data mutation logic from rendering. The useNavigation Hook lets components show loading states during submission. Error Handling with Try/Catch ensures the action doesn't crash on unexpected failures. You can debug actions using the Network Tab in DevTools and structured logging in the console.
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