Redirect from actions in Svelte - Mini Project: Build & Apply

Redirect from actions in Svelte

📖 Scenario: You are building a simple Svelte app with a form where users can submit their email to subscribe to a newsletter. After submitting, you want to redirect them to a thank you page.

🎯 Goal: Create a Svelte form that uses an action to handle the submission and then redirects the user to a thank you page using a redirect from the action.

📋 What You'll Learn

Create a form with an action function in a +page.server.js file

The action should receive the form data and perform a redirect

Use SvelteKit's redirect helper to redirect to /thank-you

Create a simple thank you page at /thank-you/+page.svelte

💡 Why This Matters

🌍 Real World

Redirecting users after form submissions is common in web apps, such as signups, logins, or feedback forms.

💼 Career

Understanding how to handle form submissions and redirects on the server side is essential for building interactive and user-friendly web applications.

1

Set up the form in +page.svelte

Create a Svelte component in +page.svelte with a form that has an action attribute set to an empty string. The form should have an input field with name="email" and a submit button with the text Subscribe.

Svelte

  Email:
  
  Subscribe

Hint

Remember to set the action attribute on the form to an empty string to link it to the server action.

2

Create the action function in +page.server.js

Create a file +page.server.js and export an actions object with a default async function named default that accepts an { request } parameter. Inside the function, get the form data by calling await request.formData() and extract the email field from it.

Svelte

export const actions = {
  default: async ({ request }) => {
    // Your code here
  }
};

Hint

Use await request.formData() to get the form data, then use formData.get('email') to get the email value.

3

Add redirect to the action function

Import redirect from @sveltejs/kit at the top of +page.server.js. Then, inside the default action function, after getting the email, return redirect(303, '/thank-you') to redirect the user to the thank you page.

Svelte

import { redirect } from '@sveltejs/kit';

export const actions = {
  default: async ({ request }) => {
    const formData = await request.formData();
    const email = formData.get('email');
    // Your code here
  }
};

Hint

Use throw redirect(303, '/thank-you') to perform the redirect from the action.

4

Create the thank you page

Create a new file +page.svelte inside a folder named thank-you. Inside it, write a simple message inside a <main> tag that says Thank you for subscribing!.

Svelte

Hint

Use a <main> tag with a heading inside it for the thank you message.

Practice

1. What is the purpose of using throw redirect(status, url) inside a SvelteKit action?

easy

A. To display an error message on the same page

B. To send the user to a different page after the action completes

C. To stop the server from running

D. To reload the current page without changes

Solution

1. Step 1: Understand the role of redirect in actions

   The throw redirect(status, url) command is used to send the user to a new page after an action finishes, such as after submitting a form.

2. Step 2: Identify the effect of the redirect

   This redirect changes the browser location to the given URL, guiding the user to a different page.

3. Final Answer:

   To send the user to a different page after the action completes -> Option B

4. Quick Check:

   Redirect in action = send user to new page [OK]

Hint: Redirect sends user to a new page after action finishes [OK]

Common Mistakes:

• Thinking redirect stops the server
• Confusing redirect with showing errors
• Assuming redirect reloads the same page

2. Which of the following is the correct syntax to redirect to '/dashboard' with status 303 inside a SvelteKit action?

easy

A. redirect(303, '/dashboard');

B. return redirect(303, '/dashboard');

C. throw redirect(303, '/dashboard');

D. throw new Redirect(303, '/dashboard');

Solution

1. Step 1: Recall correct redirect usage in SvelteKit actions

   In SvelteKit, to redirect from an action, you must throw the redirect, not just call or return it.

2. Step 2: Match the exact syntax

   The correct syntax is throw redirect(status, url). So throw redirect(303, '/dashboard'); is correct.

3. Final Answer:

   throw redirect(303, '/dashboard'); -> Option C

4. Quick Check:

   Redirect syntax = throw redirect(status, url) [OK]

Hint: Always use 'throw redirect' inside actions for redirects [OK]

Common Mistakes:

• Using return instead of throw
• Calling redirect without throw
• Using 'new Redirect' which is invalid

3. Given this SvelteKit action code:

import { redirect } from '@sveltejs/kit';

export const actions = {
  default: async () => {
    throw redirect(303, '/success');
  }
};

What happens when the form using this action is submitted?

medium

A. The user stays on the same page and sees no change

B. The form submission fails silently without redirect

C. A runtime error occurs because redirect cannot be thrown

D. The user is redirected to '/success' with a 303 status

Solution

1. Step 1: Analyze the action code behavior

   The action throws redirect(303, '/success'), which instructs SvelteKit to send a redirect response with status 303 to '/success'.

2. Step 2: Understand the effect on form submission

   When the form submits, the browser receives the redirect and navigates to '/success'.

3. Final Answer:

   The user is redirected to '/success' with a 303 status -> Option D

4. Quick Check:

   Throw redirect = browser navigates to new URL [OK]

Hint: Throwing redirect sends user to new URL after form submit [OK]

Common Mistakes:

• Thinking redirect throws error instead of redirecting
• Assuming user stays on same page
• Confusing redirect with silent failure

4. Identify the error in this SvelteKit action code snippet:

import { redirect } from '@sveltejs/kit';

export const actions = {
  default: async () => {
    return redirect(303, '/home');
  }
};

medium

A. Using return instead of throw for redirect

B. Missing await before redirect call

C. Incorrect import path for redirect

D. Redirect status code 303 is invalid

Solution

1. Step 1: Check how redirect should be used in actions

   In SvelteKit, redirects inside actions must be thrown, not returned.

2. Step 2: Identify the mistake in the code

   The code uses return redirect(303, '/home'); which is incorrect; it should be throw redirect(303, '/home');.

3. Final Answer:

   Using return instead of throw for redirect -> Option A

4. Quick Check:

   Redirect must be thrown, not returned [OK]

Hint: Redirect inside actions must be thrown, not returned [OK]

Common Mistakes:

• Returning redirect instead of throwing
• Forgetting to import redirect
• Using wrong status codes

5. You want to redirect users to '/profile' after a successful POST form submission using a SvelteKit action. Which status code should you use with throw redirect(status, '/profile') to follow best practices?

hard

A. 303

B. 302

C. 307

D. 301

Solution

1. Step 1: Understand HTTP redirect status codes for POST

   After a POST request, the recommended redirect status is 303, which tells the browser to perform a GET request to the new URL.

2. Step 2: Match the correct status code for SvelteKit redirect

   Using throw redirect(303, '/profile') ensures proper redirect behavior after form submission.

3. Final Answer:

   303 -> Option A

4. Quick Check:

   POST redirect status = 303 [OK]

Hint: Use 303 status for redirect after POST form submission [OK]

Common Mistakes:

• Using 301 or 302 which may cause method issues
• Using 307 which preserves method but is less common
• Not specifying status code at all