What is homology
Source = Protocol + domain name + port number
Two urls are homologous if they have exactly the same protocol, domain name, and port number
What is cross-domain
When a user requests resources of another domain name from the web page of one domain name, the domain name, port, or protocol are all different.
The json cross-domain
When we cross domains, we have to use another way to cross domains because the current browser does not support CORS (usually the poor ones who need to be compatible with IE)
So we request a JS file that will execute a callback with our data in it. The name of the callback can be randomly generated and passed to the background as a callback. The background will return the function to us again and execute it
Advantages: The biggest advantage is compatible with IE, cross – domain
Disadvantages:
- Since it’s a script tag, it doesn’t read ajax’s exact status code, nor does it know the response headers, so it can only listen for success or failure with onload and onError.
- Since it is a script tag, only GET requests can be sent. Post is not supported
CORS cross-domain
By default, browsers cannot access data from different sources (to protect user privacy)
But if you really want the two sites to visit each other, you need CORS
How to do?
Just write the site you want to allow in the response header of the resource being accessed
Access-Control-Allow-Origin: foo.example
Copy the codePerfect solution in one sentence
Disadvantages:
It is not compatible with IE, so IE will use JSONP