How Can I Persist Variables Across Page Loads in a Stateless HTTP Environment?

Persisting Variables Between Page Loads

HTTP being stateless, retaining values across page reloads requires external storage. Here's how to overcome this limitation:

Query String

On form submission via GET, the query string (?parameter=value) carries form field data. Set a hidden field's value accordingly:

<form method="GET">
    <input type="hidden" name="clicked" value="true" />
    <input type="submit" />
</form>

On page load, extract the query parameter:

function getParameterByName(name) {
    var regex = new RegExp("[\?&]" + name + "=([^&#]*)"),
        results = regex.exec(location.search);
    return results === null ? "" : decodeURIComponent(results[1].replace(/\+/g, " "));
}

var clicked = getParameterByName('clicked');

Web Storage

HTML5 provides Web Storage, allowing for browser-based data storage. SessionStorage stores data only during the current browsing session:

sessionStorage.setItem('clicked', 'true');

On page load, retrieve the stored value:

var clicked = sessionStorage.getItem('clicked');

Cookies

Cookies are primarily used for server-side data storage but can also be leveraged for client-side storage. jQuery simplifies cookie management:

$.cookie('clicked', 'true', {expires: 1}); // expires in 1 day

To read the cookie on page load:

var clicked = $.cookie('clicked');

Remember to un-set the cookie when no longer needed:

$.cookie('clicked', null);

Window.name

While not recommended, window.name can store strings across page refreshes and even domains:

window.name = "my value";

On page load, access the stored value:

var value = window.name;

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