How do I preserve variable values between HTML files?

Let's say I have a page that refers to a .js file. In that file I have the following code that sets the value 开发者_开发问答of a variable:

var foo;

function bar()
    {
    foo = //some value generated by some type of user input
    }

bar();

Now I'd like to be able to navigate to another page that refers to the same script, and have this variable retain the value set by bar(). What's the best way to transport the value of this variable, assuming the script will be running anew once I arrive on the next page?

You can use cookies.

Cookies were originally invented by Netscape to give 'memory' to web servers and browsers. The HTTP protocol, which arranges for the transfer of web pages to your browser and browser requests for pages to servers, is state-less, which means that once the server has sent a page to a browser requesting it, it doesn't remember a thing about it. So if you come to the same web page a second, third, hundredth or millionth time, the server once again considers it the very first time you ever came there.

This can be annoying in a number of ways. The server cannot remember if you identified yourself when you want to access protected pages, it cannot remember your user preferences, it cannot remember anything. As soon as personalization was invented, this became a major problem.

Cookies were invented to solve this problem. There are other ways to solve it, but cookies are easy to maintain and very versatile.

See: http://www.quirksmode.org/js/cookies.html

You can pass the value in the query string.
When the user navigate to the other page append the value to the query string and load it in the next.

Another option is jStorage. jStorage is probably better used for cached data and lossy user preferences (e.g. saved username in a login form), as it doesn't have full browser support (but IE6+ and most other common browsers support it) and cannot be relied upon (like cookies).

You can use YUI's Cookie Library http://developer.yahoo.com/yui/cookie/