Redirect responses in NestJS

Introduction

Redirect responses send users to a different URL automatically. This helps guide users to the right page without them clicking links.

After a user logs in, send them to their dashboard page.

When a page is moved, redirect visitors to the new location.

Send users to a login page if they try to access a protected route.

After submitting a form, redirect to a confirmation page.

Redirect from a root URL to a main homepage.

Syntax

NestJS

import { Controller, Get, Res } from '@nestjs/common';
import { Response } from 'express';

@Controller()
export class AppController {
  @Get('old-path')
  redirectToNew(@Res() res: Response) {
    return res.redirect('/new-path');
  }
}

Use the @Res() decorator to access the response object.

Call res.redirect() with the URL to send a redirect response.

Examples

Redirects the user to the '/home' URL.

NestJS

res.redirect('/home');

Redirects with status code 301 (permanent redirect) to '/new-location'.

NestJS

res.redirect(301, '/new-location');

Redirects to an external website URL.

NestJS

res.redirect('https://example.com');

Sample Program

This controller has two routes. Visiting '/old-page' sends a redirect response to '/new-page'. Visiting '/new-page' shows a welcome message.

NestJS

import { Controller, Get, Res } from '@nestjs/common';
import { Response } from 'express';

@Controller()
export class RedirectController {
  @Get('old-page')
  redirectToNewPage(@Res() res: Response) {
    return res.redirect('/new-page');
  }

  @Get('new-page')
  newPage() {
    return 'Welcome to the new page!';
  }
}

Important Notes

Using @Res() disables automatic response handling, so you must send the response yourself.

Redirect status codes like 301 (permanent) or 302 (temporary) can be specified as the first argument.

Always test redirects in a browser or with tools like curl to confirm behavior.

Summary

Redirect responses send users to a different URL automatically.

Use res.redirect() inside a controller method with @Res().

You can specify the redirect URL and optionally the status code.

Practice

1. What is the primary purpose of using res.redirect() in a NestJS controller?

easy

A. To send the user to a different URL automatically

B. To send JSON data as a response

C. To handle database queries

D. To log user requests

Solution

1. Step 1: Understand the function of res.redirect()

   This method is used to send an HTTP redirect response to the client, telling the browser to go to a different URL.

2. Step 2: Compare with other options

   Options A, B, and C describe other unrelated tasks like logging, sending JSON, or querying databases, which are not the purpose of res.redirect().

3. Final Answer:

   To send the user to a different URL automatically -> Option A

4. Quick Check:

   Redirect means sending user to another URL [OK]

Hint: Redirect means sending user to a new URL [OK]

Common Mistakes:

• Confusing redirect with sending JSON response
• Thinking redirect handles database operations
• Assuming redirect logs requests

2. Which of the following is the correct way to inject the response object to use res.redirect() in a NestJS controller method?

easy

A. Use @Body() decorator

B. Use @Req() decorator

C. Use @Res() decorator

D. Use @Param() decorator

Solution

1. Step 1: Identify the decorator for response object

   In NestJS, @Res() is used to inject the response object to access methods like redirect().

2. Step 2: Verify other decorators

   @Req() is for request, @Body() is for request body data, and @Param() is for route parameters, none provide the response object.

3. Final Answer:

   Use @Res() decorator -> Option C

4. Quick Check:

   Response object injection = @Res() [OK]

Hint: Use @Res() to get response object for redirect [OK]

Common Mistakes:

• Using @Req() instead of @Res() for response
• Confusing @Body() with response injection
• Using @Param() which is for route params

3. Consider this NestJS controller method:

async redirectToGoogle(@Res() res) {
  res.redirect('https://google.com');
}

What will happen when this method is called?

medium

A. The user will be redirected to 'https://google.com' with status 302

B. The user will receive a JSON response with the URL

C. The server will throw an error because status code is missing

D. Nothing happens because redirect needs a status code

Solution

1. Step 1: Understand default behavior of res.redirect()

   When called with only a URL, res.redirect() sends a 302 status code by default, redirecting the user to the given URL.

2. Step 2: Check if status code is mandatory

   Status code is optional; if omitted, 302 is used automatically, so no error occurs.

3. Final Answer:

   The user will be redirected to 'https://google.com' with status 302 -> Option A

4. Quick Check:

   Redirect URL alone defaults to 302 status [OK]

Hint: Redirect without status defaults to 302 [OK]

Common Mistakes:

• Thinking status code is required for redirect
• Expecting JSON response instead of redirect
• Assuming server error without status code

4. Identify the error in this NestJS controller method:

@Get('go')
async go(@Res() res) {
  res.redirect(301, 'https://example.com');
  return 'Redirecting';
}

medium

A. Status code 301 is invalid for redirect

B. Returning a string after res.redirect() causes an error

C. Missing await before res.redirect()

D. res.redirect() must be called without parameters

Solution

1. Step 1: Understand res.redirect() behavior

   Calling res.redirect() sends the response immediately. Returning a value after sending response causes NestJS to throw an error because response is already sent.

2. Step 2: Check other options

   Status code 301 is valid for permanent redirect, no await needed as redirect is synchronous, and redirect requires parameters.

3. Final Answer:

   Returning a string after res.redirect() causes an error -> Option B

4. Quick Check:

   Don't return after sending response [OK]

Hint: Don't return after res.redirect() sends response [OK]

Common Mistakes:

• Thinking 301 is invalid status code
• Adding await unnecessarily
• Calling redirect without parameters

5. You want to create a NestJS controller method that redirects users to different URLs based on a query parameter type. If type is 'admin', redirect to '/admin/dashboard' with status 302; if 'user', redirect to '/user/home' with status 301; otherwise, redirect to '/' with status 302. Which code snippet correctly implements this?

hard

A. async redirect(@Query('type') type: string, @Res() res) {
if (type === 'admin') {
return res.redirect('/admin/dashboard');
} else if (type === 'user') {
return res.redirect(301, '/user/home');
} else {
return res.redirect('/');
}
}

B. async redirect(@Query('type') type: string, @Res() res) {
if (type === 'admin') {
res.redirect(302, '/admin/dashboard');
} else if (type === 'user') {
res.redirect('/user/home');
} else {
res.redirect(302, '/');
}
return 'Redirected';
}

C. async redirect(@Query('type') type: string, @Res() res) {
if (type === 'admin') {
return res.redirect(302, '/admin/dashboard');
} else if (type === 'user') {
return res.redirect('/user/home');
} else {
return res.redirect(302, '/');
}
}

D. async redirect(@Query('type') type: string, @Res() res) {
if (type === 'admin') {
res.redirect('/admin/dashboard');
} else if (type === 'user') {
res.redirect(301, '/user/home');
} else {
res.redirect('/');
}
}

Solution

1. Step 1: Check correct usage of res.redirect()

   Calling res.redirect() with URL only defaults to 302 status. To specify status, pass it as first argument. The method sends response immediately, so no return is needed.

2. Step 2: Analyze each option

   async redirect(@Query('type') type: string, @Res() res) { if (type === 'admin') { return res.redirect('/admin/dashboard'); } else if (type === 'user') { return res.redirect(301, '/user/home'); } else { return res.redirect('/'); } } incorrectly uses return res.redirect(), which can cause errors. async redirect(@Query('type') type: string, @Res() res) { if (type === 'admin') { res.redirect(302, '/admin/dashboard'); } else if (type === 'user') { res.redirect('/user/home'); } else { res.redirect(302, '/'); } return 'Redirected'; } returns a string after redirect, causing errors. async redirect(@Query('type') type: string, @Res() res) { if (type === 'admin') { return res.redirect(302, '/admin/dashboard'); } else if (type === 'user') { return res.redirect('/user/home'); } else { return res.redirect(302, '/'); } } mixes return and missing status codes. async redirect(@Query('type') type: string, @Res() res) { if (type === 'admin') { res.redirect('/admin/dashboard'); } else if (type === 'user') { res.redirect(301, '/user/home'); } else { res.redirect('/'); } } calls res.redirect() properly without return and uses correct status codes.

3. Final Answer:

   The code that calls res.redirect() properly without return and with correct status codes -> Option D

4. Quick Check:

   Call res.redirect() without return, specify status if needed [OK]

Hint: Call res.redirect() without return; specify status as first argument [OK]

Common Mistakes:

• Returning after res.redirect() causing errors
• Not specifying status code correctly
• Returning strings after sending response