First, homologous
The so-called homologous, that is, agreements, domain name, the port number must be consistent!
If the above three, appears to have a different browser will trigger the "same origin policy."
Second, the same-origin policy
In the case where the protocol, the domain name, port number of inconsistencies, prohibition of data interaction between each other.
Purpose: To data security.
No homology between the policy server. --(proxy)
Third, cross-domain
Refers to the browser can not execute scripts other sites. Request interface is not homologous, but any access to, so you have to solve cross-domain problems. The solution of the cross-domain: . 1 .jsonp Cross-domain (which is a method, not a function of the type of method, is a means, not the same thing and json) 2 .cors It is commonly used in the cross-domain server. 3. Acting: (forward proxy, reverse proxy)