Homologous strategy, surface longitude

The same origin policy limits how documents or scripts loaded from the same source interact with resources from another source . This is an important security mechanism for browsers to isolate potentially malicious files . Homology means ：**protocol（ agreement ）、domain（ domain name ）、port（ port ）** It has to be consistent .

The homologous policy mainly limits three aspects ：

• Under the current domain js Scripts cannot access... In other domains cookie、localStorage and indexDB.
• Under the current domain js The script can't access the... In other domains DOM.
• Under the current domain ajax Unable to send cross domain request .

The purpose of homologous policy is to ensure the information security of users , It's just right js A limitation of scripts , It's not a limitation on browsers , For general img、 perhaps script Script requests will not have cross domain restrictions , This is because these operations will not perform operations that may cause security problems through the response results