document ready extracted from jQuery source

jquery.document.ready.js

/**
 * Minified version
 * 1.14KB (377 bytes gzipped)
 * 
 * (function(){var documentIsReady=false;function documentReadyHandler(fn){if(!documentIsReady){documentIsReady=true;if(document.addEventListener)document.removeEventListener("DOMContentLoaded",function(){documentReadyHandler(fn)},false);else if(document.attachEvent)if(document.readyState=="complete")document.detachEvent("onreadystatechange",function(){documentReadyHandler(fn)});fn()}}function documentReady(fn){if(document.addEventListener){document.addEventListener("DOMContentLoaded",function(){documentReadyHandler(fn)},false);window.addEventListener("load",function(){documentReadyHandler(fn)},false)}else if(document.attachEvent){document.attachEvent("onreadystatechange",function(){documentReadyHandler(fn)});window.attachEvent("onload",function(){documentReadyHandler(fn)});var toplevel=false;try{toplevel=window.frameElement==null}catch(e){}if(document.documentElement.doScroll&&toplevel)doScrollCheck(function(){documentReadyHandler(fn)})}}function doScrollCheck(fn){if(documentIsReady)return;try{document.documentElement.doScroll("left")}catch(error){window.setTimeout(function(){doScrollCheck(fn)},1);return}fn()}window.$pb={documentReady:documentReady}})();
 * 
 */

/**
 * document.ready code extracted from jquery source
 * 
 * Original Version
 * 1.78KB (644 bytes gzipped)
 */
(function () {
 
    var documentIsReady = false;
 
    function documentReadyHandler(fn) {
        if (!documentIsReady) {
            documentIsReady = true;
            if (document.addEventListener) {
                document.removeEventListener("DOMContentLoaded", function () {
                    documentReadyHandler(fn);
                }, false);
            }
            else if (document.attachEvent) {
                if (document.readyState == "complete") {
                    document.detachEvent("onreadystatechange", function () {
                        documentReadyHandler(fn);
                    });
                }
            }
            fn();
        }
    }
 
    function documentReady(fn) {
        // Mozilla, Opera and webkit nightlies currently support this event
        if (document.addEventListener) {
            // Use the handy event callback
            document.addEventListener("DOMContentLoaded", function () {
                documentReadyHandler(fn);
            }, false);
 
            // A fallback to window.onload, that will always work
            window.addEventListener("load", function () {
                documentReadyHandler(fn);
            }, false);
 
            // If IE event model is used
        } else if (document.attachEvent) {
            // ensure firing before onload,
            // maybe late but safe also for iframes
            document.attachEvent("onreadystatechange", function () {
                documentReadyHandler(fn);
            });
 
            // A fallback to window.onload, that will always work
            window.attachEvent("onload", function () {
                documentReadyHandler(fn);
            });
 
            // If IE and not a frame
            // continually check to see if the document is ready
            var toplevel = false;
 
            try {
                toplevel = window.frameElement == null;
            } catch (e) { }
 
            if (document.documentElement.doScroll && toplevel) {
                doScrollCheck(function () {
                    documentReadyHandler(fn);
                });
            }
        }
    }
 
    function doScrollCheck(fn) {
        if (documentIsReady) {
            return;
        }
        try {
            // If IE is used, use the trick by Diego Perini
            // http://javascript.nwbox.com/IEContentLoaded/
            document.documentElement.doScroll("left");
        } catch (error) {
            window.setTimeout(function () {
                doScrollCheck(fn);
            }, 1);
            return;
        }
 
        fn();
    }
 
    window.$pb = {documentReady:documentReady};
})();
 
$pb.documentReady(function () {
  alert('hi');
});