h5-- local storage sessionStorage, localstorage

Respective advantages and scene of several storage methods

• storage特点（sessionStorage，localStorage）：

1. 1. The storage capacity of 5M
   2. The client is complete, the server will not process requests
   3. sessionStorage data is not shared, localStorage share,
   4. api same

      1. getItem // fetch record

      2. setIten // Set Record

      3. removeItem // remove records

      4. // key takes a value corresponding to the key

      5. clear // Clear History

   5. Memory contents
      1. Long as it is a sequence of the contents may be stored into a string

sessionStorage:

1. 1. Act on the current page, a new page to open or close the page when the data disappeared;
   2. Different browser window data is not shared

localStorage:

1. 1. There is always, unless manually deleted,
   2. Different browser data sharing

If data have modified or deleted, it will trigger an event storage

 

    On the window object data change is not triggered

Note: session with the window can, example: iframe operation

   window.addEventListener ( 'Storage', function (E) { 
            the console.log (e.key) // modify or delete the key value 
            console.log (e.newValue) // value newly stored 
            console.log (e.oldValue ) // call the value before the change 
            console.log (e.storageArea) // current storage objects 
            console.log (e.url) // url of the document that triggered the change of script 
         });　

• cookie：
  

1. characteristic

   1. cookie can implement cross-page global variables 
      cookie can span multiple pages under the same domain name, but can not span multiple domains make! use 
      the same website all the pages share a cookie 
      you can set expiration date 
      storage space around 4-10KB

2. Common applications:

   1. Save the user login status;

   2. Track user behavior;

   3. Custom page;

   4. Create a shopping cart and so on ...　

3. Shortcoming

   1. cookie may be disabled;
   2. cookie associated with the browser, you can not visit each other;
   3. the user cookie may be deleted;
   4. cookie security is not high enough; 
   5. cookie storage space is very small (only about 4-10KB)