This small script:

• Finds all media query rules in any stylesheets on a page
• For each of those MediaRules creates a MatchMedia thingy
• Adds a listener to each MatchMedia object
• Calls a provided changeMediaHandler each time a MatchMedia event fires
• Is a work in progress

The mqEvents function is attached to the window object, which it probably should not be.

Run mqEvents().

Pass it a single function parameter that will run each time a MatchMedia event fires. The function will be passed the MediaQueryList from the event.

mqEvents(function (mql) {
    if (mql.matches) {
        // Media query condition was met
    }
    else {
        // Media query condition was not met
    }
});

• document.styleSheets - https://developer.mozilla.org/en/Document_Object_Model_(DOM)/document.styleSheets
• window.matchMedia - https://developer.mozilla.org/en/DOM/window.matchMedia
• CSSMediaRule - https://developer.mozilla.org/en/DOM/cssMediaRule
• Get the name of an object type - http://stackoverflow.com/questions/332422/how-do-i-get-the-name-of-an-objects-type-in-javascript