jquery.pagevisibility.js

/*! jquery.pagevisibility v0.2.2 | (c) 2013 Daniel Herman | opensource.org/licenses/MIT */
(function (factory) {
    if ( typeof define === "function" && define.amd ) {
        // AMD. Register as an anonymous module.
        define([ "jquery" ], factory );
    } else {
        // Browser globals
        factory( jQuery );
    }
}(function( $ ) {
    "use strict";

    var prefix, prefixes, polyfillHidden, visibilityState, supportsVisibilityApi, hiddenProperty, defineProp, document;

    document = window.document;
    defineProp = Object.defineProperty || $.noop;
    supportsVisibilityApi = false;
    prefixes = [ "ms", "moz", "webkit", "" ];

    while( prefixes.length ) {
        prefix = prefixes.pop();
        hiddenProperty = prefix ? prefix + "Hidden" : "hidden";

        if ( hiddenProperty in document ) {
            supportsVisibilityApi = true;
            break;
        }
    }

    if ( !supportsVisibilityApi ) {
        // Add a good enough unprefixed polyfill for browsers that don't support the visibility API
        // and set the initial values.
        polyfillHidden = document.hidden = false;
        visibilityState = document.visibilityState = "visible";

        // Support: Android < 4
        // http://bugs.jquery.com/ticket/13494
        // http://caniuse.com/#feat=pagevisibility
        try {
            defineProp( document, "hidden", {
                get: function() {
                    return polyfillHidden;
                },
                set: $.noop
            });

            defineProp( document, "visibilityState", {
                get: function() {
                    return visibilityState;
                },
                set: $.noop
            });
        }
        catch ( e ) {}

        $( window ).bind( "focus blur", function( e ) {
            var shouldBeHidden = e.type === "blur";

            if ( polyfillHidden !== shouldBeHidden ) {

                // In browsers that support Object.defineProperty,
                // setting the two properties on document is essentially a no-op.
                // In other older browsers, this is how we'll keep the properties in sync,
                // although it's more prone to tampering than with Object.defineProperty.
                document.hidden = polyfillHidden = shouldBeHidden;
                document.visibilityState = visibilityState = shouldBeHidden ? "hidden" : "visible";

                $( document ).trigger( "visibilitychange" );
            }
        });
    }
    else if ( prefix ) {
        // If we're dealing with a prefixed version of the API, then
        // normalize it so that we can use the same API across browsers.
        $.event.special.visibilitychange = {
            bindType: prefix + "visibilitychange"
        };

        defineProp( document, "hidden", {
            get: function() {
                return document[ hiddenProperty ];
            }
        });

        defineProp( document, "visibilityState", {
            get: function() {
                return document[ prefix + "VisibilityState" ];
            }
        });
    }
}));