One. What Ajax is: 1. With asynchronous mode, the user experience is improved by 2. Optimizes the transfer between browser and server, reduces unnecessary data round-trip, and reduces bandwidth consumption by 3. Ajax runs on the client side, assuming some of the work that would otherwise have been done by the server, reducing the load on the server under a large user volume. The biggest features of ajax: 1. Ajax can implement dynamic non-flush (partial refresh) 2. The ReadyState attribute state has 5 desirable values: 0 = uninitialized, 1 = start, 2 = send, 3 = receive, 4 = completion ajax synchronous and Asynchronous differences: 1. Synchronization: Submit request, wait for server processing, processing finished return, this period client browser can not do anything 2. Asynchronous: Request through event triggering server processing (this is what the browser can still do)--and the 3rd parameter in the Ajax.open method is set to synchronous or asynchronous. Disadvantages of ajax: 1. Ajax does not support browser Back button 2. Security issues Ajax exposes the details of the interaction with the server 3. Support for search engines is weaker by 4. Breaking the program's exception mechanism 5. Not easy to debug troubleshoot cross-domain issues: 1. Jsonp2. Iframe3. Window.name, Window.postmessage4. Set Proxy page two on the server. HTTP status Code Continue continue, usually when the post request is sent, the HTTP header is sent after the server will return this information, indicating confirmation, and then send the specific parameter information, OK Normal return information 201 Created & nbsp; the request was successful and the server created a new resource 202 Accepted The server has accepted the request but has not processed 301 Moved permanently requested page has been permanently moved to the new location 302 Found Temporary REDIRECT 303 see other temporary redirect, and always use GET to request new URI304 not Modified The requested Web page has not been modified since the last request the request Server does not understand the request Format, the client should not attempt to use the same content again to initiate the request 401 unauthorized request unauthorized 403 Forbidden Disable access 404 Not Found Unable to find a resource that matches the URI. Internal Server error Most common server-side errors 503 Service unavailable server side temporarily fails to process requests (may be overloaded or maintained)
What is
Ajax? An interactive model of Ajax? What is the difference between synchronous and asynchronous? How do I troubleshoot cross-domain issues? and the HTTP status code
