[javascript] Persist javascript variables across pages?

Is there a way we can persist javascript variables across various pages? Suppose in Page A I am setting window.someVar = 5. Then I move to Page B, via clicking a hyperlink in A, and do something like alert(window.someVar) -- I should get a message box displaying 5. Is there a technique to persist someVar as such...?

I recommend web storage. Example:

// Storing the data: localStorage.setItem("variableName","Text"); // Receiving the data: localStorage.getItem("variableName");

Just replace variable with your variable name and text with what you want to store. According to W3Schools, it's better than cookies.

Yes, using Cookies. But be careful, don't put too much in them (I think there is a limit at 4kb). But a few variables are ok.

If you need to store considerably more than that, check out @Annie's great tips in the other answer. For small time data storage, I would say Cookies are the easiest thing.

Note that cookies are stored client side.

You can persist values using HTML5 storage, Flash Storage, or Gears. The dojo storage library provides a nice wrapper for this.

You can use http://rhaboo.org as a wrapper around localStorage. It stores complex objects but doesn't merely stringify and parse the whole thing like most such libraries do. That's really inefficient if you want to store a lot of data and add to it or change it in small chunks. Also, JSON discards a lot of important stuff like non-numerical properties of arrays.

In rhaboo you can write things like this:

var store = Rhaboo.persistent('Some name');

store.write('count', store.count ? store.count+1 : 1);

var laststamp = store.stamp ? store.stamp.toString() : "never";
store.write('stamp', new Date());

store.write('somethingfancy', {
  one: ['man', 'went'],
  2: 'mow',
  went: [  2, { mow: ['a', 'meadow' ] }, {}  ]
});

store.somethingfancy.went[1].mow.write(1, 'lawn');
console.log( store.somethingfancy.went[1].mow[1] ); //says lawn

BTW, I wrote rhaboo

I would recommend you to give a look to this library:

• PersistJS

I really like it, it supports a variety of storage backends (from cookies to HTML5 storage, Gears, Flash, and more...), its usage is really transparent, you don't have to know or care which backend is used the library will choose the right storage backend depending on the browser capabilities.

For completeness, also look into the local storage capabilities & sessionStorage of HTML5. These are supported in the latest versions of all modern browsers, and are much easier to use and less fiddly than cookies.

http://www.w3.org/TR/2009/WD-webstorage-20091222/

https://www.w3.org/TR/webstorage/. (second edition)

Here are some sample code for setting and getting the values using sessionStorage and localStorage :

 // HTML5 session Storage
 sessionStorage.setItem("variableName","test");
 sessionStorage.getItem("variableName");


//HTML5 local storage 
localStorage.setItem("variableName","Text");
// Receiving the data:
localStorage.getItem("variableName");