Write cookies, sessionstorage, localstorage and session at will

• cookie：

1. It can be set at the back end or at the front end
   
2. By default, it is valid before the browser is closed , You can set the expiration time
3. According to the back-end requirements, it will be in ajax By default, the request header of carries the delivery , There is no need to set too many front-end
4. Size limit 4KB.

• sessionStorage：

1. Pure front-end settings
   
2. “ This session ” It is valid inside and cannot be stored for a long time
3. With or without ajax Request delivery 、 How to deliver 、 What is passed is controlled by the front end
4. Storage size 5M.

• localStorage

1. Pure front-end settings
   
2. Long term effectiveness , Users may not pass js Cleanup will always exist
3. With or without ajax Request delivery 、 How to deliver 、 What is passed is controlled by the front end
4. Storage size 5M.

The attention of the above three stored in the client has the same source protection strategy ~（

emm Homology protection strategy is a kind of security behavior of browser , It is to prevent different sites from illegally obtaining the data stored by users Leakage of verification information .

http://localhost:8888  Take this as an example

http:// It's the name of the agreement

localhost This part is domain name The corresponding is www.xxxx.com This part

:8888 It's the port number

If there are different parts of the above three, it will be considered that they are not the same site and cannot obtain the data stored in other sites . Not much writing Write another one when you have time .

）

• session 

1. Pure backend cache , Not in the front
2. The validity period is controlled by the back end
3. What the programmer sets himself Controllability Use restrictions are controlled by your own settings . Not much introduction