$(document).ready() source

Question

I need to wait for document readyness in my JavaScript, to insert a div at the bottom of the body.

I want to:

• make this JavaScript file as small as possible (compile it down to < 1kb if possible)
• inline the code that provides the document readyness in a closure (without exporting it)

Inlining the whole jQuery source in my file would be too big, so I'm looking for other methods. window.onload would work, but I specifically want document readyness, and not wait for the window.onload event.

Does anyone know a JS snippet that can do this? Or should I just copy part of jQuery's source?

EDIT:

I managed to crawl the jQuery source and put together with the following snippet:

var ready = (function () {
    var ready_event_fired = false;
    var ready_event_listener = function (fn) {

        // Create an idempotent version of the 'fn' function
        var idempotent_fn = function () {
            if (ready_event_fired) {
                return;
            }
            ready_event_fired = true;
            return fn();
        }

        // The DOM ready check for Internet Explorer
        var do_scroll_check = function () {
            if (ready_event_fired) {
                return;
            }

            // If IE is used, use the trick by Diego Perini
            // http://javascript.nwbox.com/IEContentLoaded/
            try {
                document.documentElement.doScroll('left');
            } catch(e) {
                setTimeout(do_scroll_check, 1);
                return;
            }

            // Execute any waiting functions
            return idempotent_fn();
        }

        // If the browser ready event has already occured
        if (document.readyState === "complete") {
            return idempotent_fn()
        }

        // Mozilla, Opera and webkit nightlies currently support this event
        if (document.addEventListener) {

            // Use the handy event callback
            document.addEventListener("DOMContentLoaded", idempotent_fn, false);

            // A fallback to window.onload, that will always work
            window.addEventListener("load", idempotent_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", idempotent_fn);

            // A fallback to window.onload, that will always work
            window.attachEvent("onload", idempotent_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) {
                return do_scroll_check();
            }
        }
    };
    return ready_event_listener;
})();

// TEST
var ready_1 = function () {
    alert("ready 1");
};
var ready_2 = function () {
    alert("ready 2");
};
ready(function () {
    ready_1();
    ready_2();
});

Thank you very much for helping me find this in the jQuery source. I can now put all this in a closure and do my work without exporting any functions and polluting the global scope.

Answer 1

One option would be to just get the core.js jQuery file from github.

You could probably slim it down quite a bit for code you don't need. Then run it through YUI compressor, and it should be pretty small.

• http://github.com/jquery/jquery/blob/1.4.2/src/core.js (jQuery core)
• http://yui.2clics.net/ (YUI compressor online)

I tried it, and this code worked properly:

$(function() {
    var newDiv = document.createElement('div');
    document.getElementsByTagName('body')[0].appendChild(newDiv);
});

---

Update: This was as small as I got it. It is entirely from jQuery and is around 1,278 bytes (compressed). Should get smaller when you gzip.

Only difference is that you need to call it like:

$.fn.ready(function() {
    // your code
});

YUI Compressed:

(function(){var e=function(i,j){},c=window.jQuery,h=window.$,d,g=false,f=[],b;e.fn={ready:function(i){e.bindReady();if(e.isReady){i.call(document,e)}else{if(f){f.push(i)}}return this}};e.isReady=false;e.ready=function(){if(!e.isReady){if(!document.body){return setTimeout(e.ready,13)}e.isReady=true;if(f){var k,j=0;while((k=f[j++])){k.call(document,e)}f=null}if(e.fn.triggerHandler){e(document).triggerHandler("ready")}}};e.bindReady=function(){if(g){return}g=true;if(document.readyState==="complete"){return e.ready()}if(document.addEventListener){document.addEventListener("DOMContentLoaded",b,false);window.addEventListener("load",e.ready,false)}else{if(document.attachEvent){document.attachEvent("onreadystatechange",b);window.attachEvent("onload",e.ready);var i=false;try{i=window.frameElement==null}catch(j){}if(document.documentElement.doScroll&&i){a()}}}};d=e(document);if(document.addEventListener){b=function(){document.removeEventListener("DOMContentLoaded",b,false);e.ready()}}else{if(document.attachEvent){b=function(){if(document.readyState==="complete"){document.detachEvent("onreadystatechange",b);e.ready()}}}}function a(){if(e.isReady){return}try{document.documentElement.doScroll("left")}catch(i){setTimeout(a,1);return}e.ready()}window.jQuery=window.$=e})();

---

Full source (again, this is jQuery code):

(function() {
var jQuery = function( selector, context ) {
    },
    _jQuery = window.jQuery,
    _$ = window.$,

    rootjQuery,
    readyBound = false,
    readyList = [],
    DOMContentLoaded;

jQuery.fn = {
    ready: function( fn ) {
        jQuery.bindReady();
        if ( jQuery.isReady ) {
            fn.call( document, jQuery );
        } else if ( readyList ) {
            readyList.push( fn );
        }
        return this;
    }
};
jQuery.isReady = false;
jQuery.ready = function() {
        if ( !jQuery.isReady ) {
            if ( !document.body ) {
                return setTimeout( jQuery.ready, 13 );
            }
            jQuery.isReady = true;
            if ( readyList ) {
                var fn, i = 0;
                while ( (fn = readyList[ i++ ]) ) {
                    fn.call( document, jQuery );
                }
                readyList = null;
            }
            if ( jQuery.fn.triggerHandler ) {
                jQuery( document ).triggerHandler( "ready" );
            }
        }
    };
jQuery.bindReady = function() {
        if ( readyBound ) {
            return;
        }
        readyBound = true;

        if ( document.readyState === "complete" ) {
            return jQuery.ready();
        }
        if ( document.addEventListener ) {
            document.addEventListener( "DOMContentLoaded", DOMContentLoaded, false );
            window.addEventListener( "load", jQuery.ready, false );
        } else if ( document.attachEvent ) {

            document.attachEvent("onreadystatechange", DOMContentLoaded);
            window.attachEvent( "onload", jQuery.ready );

            var toplevel = false;
            try {
                toplevel = window.frameElement == null;
            } catch(e) {}
            if ( document.documentElement.doScroll && toplevel ) {
                doScrollCheck();
            }
        }
    };
rootjQuery = jQuery(document);
if ( document.addEventListener ) {
    DOMContentLoaded = function() {
        document.removeEventListener( "DOMContentLoaded", DOMContentLoaded, false );
        jQuery.ready();
    };
} else if ( document.attachEvent ) {
    DOMContentLoaded = function() {
        if ( document.readyState === "complete" ) {
            document.detachEvent( "onreadystatechange", DOMContentLoaded );
            jQuery.ready();
        }
    };
}
function doScrollCheck() {
    if ( jQuery.isReady ) {
        return;
    }
    try {

        document.documentElement.doScroll("left");
    } catch(e) {
        setTimeout( doScrollCheck, 1 );
        return;
    }
    jQuery.ready();
}
window.jQuery = window.$ = jQuery;
})();

I'm sure there are more bytes that could be removed.

Don't forget:

/*!
 * jQuery JavaScript Library v1.4.2
 * http://jquery.com/
 *
 * Copyright 2010, John Resig
 * Dual licensed under the MIT or GPL Version 2 licenses.
 * http://jquery.org/license
*/

Answer 2

There are several implementations for "DOMReady" functions but most that I can find seem a bit dated, so I don't know how they will behave with IE8 and such.

I would recommend using jQuery's ready() as I think it promises the most cross-browser compatibility. I'm not an expert in jQuery's source code, but this seems to be the right spot (lines 812-845 or search for function bindReady).