Single file upload in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the multer middleware in Express?

Multer is used to handle file uploads in Express apps. It processes incoming files and stores them temporarily or permanently.

beginner

How do you configure multer to accept a single file upload with the field name 'avatar'?

Use upload.single('avatar') where upload is the multer instance. This tells multer to expect one file with the field name 'avatar'.

beginner

What does req.file contain after a successful single file upload?

req.file holds information about the uploaded file like its original name, size, encoding, and the path where it was saved.

intermediate

Why is it important to handle errors when uploading files in Express?

Errors can happen if the file is too large, the wrong type, or the upload fails. Handling errors helps keep the app stable and informs users what went wrong.

intermediate

What is a simple way to limit the size of uploaded files using multer?

Set the limits.fileSize option in multer configuration to restrict the maximum file size allowed.

Which middleware is commonly used for handling single file uploads in Express?

A multer

B body-parser

C cors

D express-session

Multer is designed specifically for handling multipart/form-data, which is used for file uploads.

What does upload.single('photo') do in an Express route?

A Blocks file uploads

B Accepts multiple files with any field name

C Accepts one file with the field name 'photo'

D Uploads files to a cloud service automatically

It tells multer to expect a single file upload with the field name 'photo'.

Where can you find the uploaded file's information after multer processes it?

A req.file

B req.body.file

C req.files

D req.upload

req.file contains the uploaded file's details for single file uploads.

How can you limit the size of an uploaded file using multer?

A Use express.static middleware

B Set the limits.fileSize option

C Set maxUploadSize in Express settings

D Use body-parser size limit

Multer's configuration allows setting limits.fileSize to restrict file size.

What happens if a file larger than the limit is uploaded with multer?

A The file uploads but is truncated

B The server crashes

C The file uploads normally without issues

D An error is thrown and can be caught in error handling

Multer throws an error when the file size exceeds the limit, which should be handled properly.

Explain how to set up a simple Express route to handle a single file upload using multer.

Think about the steps from importing multer to accessing the file in the route.

Describe why handling errors during file upload is important and how you might do it in Express with multer.

Consider what can go wrong and how to keep the app stable.