Express.js Course
Express.js
/
Beginner

CORS

Definition

Cross-Origin Resource Sharing (CORS) is a browser security feature that restricts cross-origin HTTP requests. If your React app is on `localhost:3000` and your Express API is on `localhost:5000`, the browser will block requests unless Express explicitly sends CORS headers.

Explain Like I'm New

Cross-Origin Resource Sharing (CORS) is a browser security feature that restricts cross-origin HTTP requests.

Interactive Example

Loading...
Console output will appear here...

Interview Questions

basic

  • What is the primary purpose of CORS in Express.js?
  • How do you initialize CORS?

intermediate

  • How does CORS integrate with other middleware components?
  • Can you explain a common use case for CORS?

advanced

  • What are the performance implications of CORS in a high-traffic production application?
  • How would you debug issues related to CORS?

trick

  • Is it possible to achieve the same result as CORS without using Express?

Flash Cards

Question

Define CORS in your own words.

Click to reveal answer
Answer

Cross-Origin Resource Sharing (CORS) is a browser security feature that restricts cross-origin HTTP requests.

Question

When should you avoid using CORS?

Click to reveal answer
Answer

It depends on the specific architectural requirements and performance bottlenecks of your application. Overusing it can sometimes lead to tightly coupled code.