JS how to cache a variable

Question

What I want to do is to be able to create a variable  give it a value  close and reopen the window  and be able to retrieve the value I set in the last session  What is the simplest way to do that  JQuery answers are welcome

User · Accepted Answer

Use localStorage for that  It s persistent over sessions   Writing    localStorage  myKey      somestring      only strings   Reading    var myVar   localStorage  myKey       defaultValue     If you need to store complex structures  you might serialize them in JSON  For example    Reading    var stored   localStorage  myKey    if  stored  myVar   JSON parse stored   else myVar    a  test   b   1  2  3      Writing    localStorage  myKey     JSON stringify myVar     Note that you may use more than one key  They ll all be retrieved by all pages on the same domain   Unless you want to be compatible with IE7  you have no reason to use the obsolete and small cookies

User · Answer

You have three options    Cookies  https   developer mozilla org en-US docs DOM document cookie DOMStorage  sessionStorage or localStorage   https   developer mozilla org en-US docs DOM Storage If your users are logged in  you could persist data in your server s DB that is keyed to a user  or group

User · Answer

check out my js lib for caching  https   github com hoangnd25 cacheJS  My blog post  New way to cache your data with Javascript  Features    Conveniently use array as key for saving cache Support array and localStorage Clear cache by context  clear all blog posts with authorId  abc   No dependency   Basic usage   Saving cache   cacheJS set  blogId 1 type  view     lt h1 gt Blog 1 lt  h1 gt     cacheJS set  blogId 2 type  view     lt h1 gt Blog 2 lt  h1 gt    null   author  hoangnd     cacheJS set  blogId 3 type  view     lt h1 gt Blog 3 lt  h1 gt    3600   author  hoangnd  categoryId 2      Retrieving cache   cacheJS get  blogId  1 type   view       Flushing cache  cacheJS removeByKey  blogId  1 type   view     cacheJS removeByKey  blogId  2 type   view      cacheJS removeByContext  author  hoangnd       Switching provider  cacheJS use  array    cacheJS use  array   set  blogId 1    lt h1 gt Blog 1 lt  h1 gt

User · Answer

You could possibly create a cookie if thats allowed in your requirment  If you choose to take the cookie route then the solution could be as follows   Also the benefit with cookie is after the user closes the Browser and Re-opens  if the cookie has not been deleted the value will be persisted   Cookie  Create and Store a Cookie    function setCookie c name value exdays    var exdate new Date    exdate setDate exdate getDate     exdays   var c value escape value      exdays  null            expires   exdate toUTCString     document cookie c name         c value      The function which will return the specified cookie   function getCookie c name    var i x y ARRcookies document cookie split       for  i 0 i lt ARRcookies length i        x ARRcookies i  substr 0 ARRcookies i  indexOf          y ARRcookies i  substr ARRcookies i  indexOf      1     x x replace    s   s   g        if  x  c name            return unescape y                 Display a welcome message if the cookie is set  function checkCookie     var username getCookie  username      if  username  null  amp  amp  username            alert  Welcome again     username       else        username prompt  Please enter your name          if  username  null  amp  amp  username                setCookie  username  username 365                 The above solution is saving the value through cookies   Its a pretty standard way without storing the value on the server side    Jquery  Set a value to the session storage   Javascript     sessionStorage   foo    data  bar        Retrieve the value     sessionStorage   foo    data  bar         sessionStorage   foo    Results   data  bar     Local Storage Now lets take a look at Local storage  Lets say for example you have an array of variables that you are wanting to persist  You could do as follows   var names     names 0  prompt  New name     localStorage  names   JSON stringify names          var storedNames JSON parse localStorage  names       Server Side Example using ASP NET  Adding to Sesion  Session  FirstName     FirstNameTextBox Text  Session  LastName     LastNameTextBox Text       When retrieving an object from session state  cast it to     the appropriate type   ArrayList stockPicks    ArrayList Session  StockPicks        Write the modified stock picks list back to session state  Session  StockPicks     stockPicks    I hope that answered your question

User · Answer

I have written a generic caching func   which will cache any variable easily and very readable format  Caching function   function calculateSomethingMaybe args       return args     function caching fn       const cache           return function            const string   arguments 0           if  cache string                const result   fn apply this  arguments               cache string    result              return result                    return cache string            const letsCache   caching calculateSomethingMaybe    console log letsCache  a book    letsCache  a pen    letsCache  a book

[javascript] JS how to cache a variable

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