#1. What are the seven-layer models of OSI?
Application layer: An interface between network services and end users.
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Presentation layer: data representation, security, and compression.
Session layer: establish, manage, and terminate sessions.
Transport layer: Define the protocol port number for transmitting data, as well as flow control and error checking.
Network layer: Perform logical address addressing to realize path selection between different networks.
Data link layer: Establish logical connections, perform hardware address addressing, error checking and other functions.
Physical layer: establishing, maintaining, and disconnecting physical connections.
2. What are the differences between get and post requests?
GET is harmless when the browser rolls back, while POST will submit the request again.
The URL address generated by GET can be Bookmarked, but POST cannot.
GET requests will be actively cached by the browser, but POST will not unless manually set.
GET requests can only be URL encoded, while POST supports multiple encoding methods.
GET request parameters will be completely retained in the browser history, while parameters in POST will not be retained.
There is a length limit on the parameters transmitted in the URL for the GET request, but there is no length limit for POST.
Regarding the data type of parameters, GET only accepts ASCII characters, while POST has no restrictions.
GET is less secure than POST because the parameters are directly exposed on the URL, so it cannot be used to pass sensitive information.
GET parameters are passed through the URL, and POST is placed in the Request body.
3. How to achieve cross-domain?
Method 1: Image ping or script tag cross-domain
Method 2: JSONP cross-domain
Method 3: CORS
Method 4: window.name iframe
Method 5: window.postMessage()
Method 6: Modify document.domain across subdomains
Method 7: WebSocket
Method 8: Proxy
4. Tell me about the JSONP implementation principle?
jsonp is json padding, which dynamically creates script tags. Using the src attribute of the script tag, you can obtain js scripts in any domain. Through this feature (it can also be said to be a loophole), the server no longer returns json. format, but returns a piece of js code that calls a certain function, and calls it in src, thus achieving cross-domain.
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