Ajax definition: the technology that allows the client browser to communicate with the server without refreshing the current page is Ajax technology.
2. The technologies that do not refresh the page and communicate with the server include Ajax, flash, Java applet, iframe, frameset and XMLHttpRequest.
Note: the framework is to put multiple pages in the framework, which is a cross page operation. It is different from the real non refresh page and server communication. Just refresh the page in a frame, and the whole page will not be refreshed.
5. Ajax implementation steps:
1) Create XMLHttpRequest object
2) Establish connection
3) Send request data to the server
4) The server responds to the client
There are also two if judgments to judge whether readyState is equal to 4, that is, the response is completed, and whether status is equal to 200, that is, everything is normal.