What is Ajax?

A: It is a set of methods provided by the browser to improve the user’s browsing experience by updating data without refreshing the page.

What kind of request does Ajax send?

A: HTTP request.

Pros and cons of Ajax

Advantages:

  1. You can communicate with the server without refreshing the page.
  2. Allows you to update parts of the page based on user events.

Disadvantages:

  1. You can’t go backwards without browsing history.
  2. Cross-domain problems exist.
  3. SEO is not friendly.

HTTP request packets

  • Line: Request modes such as GET and POST, URL parameters, and HTTP version.
  • Header: Host, Cookie, Content-Type, user-agent
  • Blank line: This is fixed, don’t care.
  • Body: If it is a GET request, this is empty. If it is a POST request, this is not empty and can be the parameter to be sent.

HTTP response packet

  • Line: HTTP protocol version, return status code, status string
  • Header: content-Type: text/ HTML, charset= UTF-8, Content-Length :2048, Content-Encoding: gzip
  • Blank line: fixed
  • Body:…