File size limits in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of setting file size limits in Express file uploads?

File size limits prevent users from uploading files that are too large, which helps protect the server from running out of memory or disk space and improves security.

beginner

How do you set a file size limit using the 'express.json()' middleware?

You set the 'limit' option in 'express.json()', for example: app.use(express.json({ limit: '1mb' })) to limit JSON payloads to 1 megabyte.

intermediate

Which middleware is commonly used in Express to handle file uploads with size limits?

The 'multer' middleware is commonly used to handle file uploads and allows setting file size limits using the 'limits' option.

intermediate

How do you configure 'multer' to reject files larger than 2MB?

You pass a 'limits' object when creating the multer instance: <code>const upload = multer({ limits: { fileSize: 2 * 1024 * 1024 } })</code>. This rejects files bigger than 2 megabytes.

intermediate

What happens if a user tries to upload a file larger than the set limit in Express with multer?

Multer throws an error with code 'LIMIT_FILE_SIZE'. You can catch this error in your route handler to send a friendly message to the user.

Which option correctly sets a 5MB limit for JSON payloads in Express?

A app.use(express.json({ sizeLimit: 5000 }))

B app.use(express.json({ maxSize: 5 }))

C app.use(express.json({ limit: '5mb' }))

D app.use(express.json({ maxPayload: '5MB' }))

The 'limit' option in express.json() sets the maximum size. '5mb' means 5 megabytes.

What middleware is best for handling file uploads with size limits in Express?

A multer

B helmet

C cors

D body-parser

'multer' is designed for handling multipart/form-data and file uploads with size limits.

How do you specify a 1MB file size limit in multer?

A maxSize: 1024

B limits: { maxFileSize: 1 }

C limit: '1mb'

D limits: { fileSize: 1 * 1024 * 1024 }

The 'fileSize' property in 'limits' expects bytes, so 1 * 1024 * 1024 equals 1MB.

What error code does multer throw when a file exceeds the size limit?

A LIMIT_FILE_SIZE

B FILE_TOO_LARGE

C SIZE_EXCEEDED

D UPLOAD_ERROR

Multer uses the error code 'LIMIT_FILE_SIZE' for files exceeding the size limit.

Why is it important to set file size limits on uploads?

A To speed up the upload process

B To prevent server overload and security risks

C To allow unlimited file uploads

D To reduce the number of users

File size limits help protect the server from overload and potential security issues.

Explain how to set and handle file size limits in Express using multer.

Think about configuring multer and catching errors.

Describe why setting file size limits is important in web applications.

Consider server health and user experience.