jQuery について知っておくべきことは何ですか?

(function( window, undefined){})(window)

undefined = true;
(function(window, document, undefined){    
    if(foo == undefined) {
        }
})(this, document)

(function(A, B, C)){
    B.getElementById('')
})(this, document)

(function loop(){
    doStuff();
    $('#update').load('awesomething.php',function(){
        loop();
    })
    //setTimeout(loop, 100)
})()

var
    // Map over jQuery in case of overwrite
    _jQuery = window.jQuery,
    // Map over the $ in case of overwrite
    _$ = window.$;
jQuery.noConflict = function( deep ) {
    if ( window.$ === jQuery ) {
        window.$ = _$;
    }
    if ( deep && window.jQuery === jQuery ) {
        window.jQuery = _jQuery;
    }
    return jQuery;
};

jQuery.extend({
    propFix: {
        "for": "htmlFor",
        "class": "className"
    },
    prop: function( elem, name, value ) {
        //...
        name = jQuery.propFix[ name ] || name;
    },
    propHooks: {
        //...
    }
});
jQuery.each([
    "tabIndex",
    "readOnly",
    "maxLength",
    "cellSpacing",
    "cellPadding",
    "rowSpan",
    "colSpan",
    "useMap",
    "frameBorder",
    "contentEditable"
], function() {
    jQuery.propFix[ this.toLowerCase() ] = this;
});

jQuery.fx.speeds = {
    slow: 600,
    fast: 200,
    // Default speed
    _default: 400
};

var isIE 
//...
jQuery.fx.speeds._default = isIE ? 800 : 400
jQuery.fx.speeds.veryfast = 200;
$('...').fadeIn('veryfast')

jQuery.ready.promise = function( obj ) {    //...省略若干        } else if ( document.addEventListener ) {            // 使用addEventListener "DOMContentLoaded" 监听ready事件            document.addEventListener( "DOMContentLoaded", completed, false );            // 备选方案 "load"            window.addEventListener( "load", completed, false );        //如果IE        } else {            // Ensure firing before onload, maybe late but safe also for iframes                        //IE下 attachEvent 的"onreadystatechange"            document.attachEvent( "onreadystatechange", completed );            // A fallback to window.onload, that will always work                        //备选方案onload            window.attachEvent( "onload", completed );            // If IE and not a frame            // continually check to see if the document is ready            var top = false;            try {                top = window.frameElement == null && document.documentElement;            } catch(e) {}            if ( top && top.doScroll ) {                (function doScrollCheck() {                    if ( !jQuery.isReady ) {                        try {                            // Use the trick by Diego Perini                            // http://javascript.nwbox.com/IEContentLoaded/                            top.doScroll("left");                        } catch(e) {                            return setTimeout( doScrollCheck, 50 );                        }                        // detach all dom ready events                        detach();                        // and execute any waiting functions                        jQuery.ready();                    }                })();            }        }    }    return readyList.promise( obj );};
.ready 利用了下面的.promise去做确保载入完成的工作，重点是document.addEventListener( "DOMContentLoaded", completed, false );window.addEventListener( "load", completed, false );document.attachEvent( "onreadystatechange", completed );window.attachEvent( "onload", completed );

jQuery = function( selector, context ) {
        // The jQuery object is actually just the init constructor 'enhanced'
        // Need init if jQuery is called (just allow error to be thrown if not included)
        return new jQuery.fn.init( selector, context );
}

// Initialize a jQuery object
    init = jQuery.fn.init = function( selector, context ) {
        var match, elem;
        // HANDLE: $(""), $(null), $(undefined), $(false)
            //超级省略...下略
        // Handle HTML strings
        // HANDLE: $(html) -> $(array)
        // HANDLE: $(html, props)
        // HANDLE: $(#id)
        // HANDLE: $(expr, $(...))
        // HANDLE: $(expr, context)
        // HANDLE: $(DOMElement)
        // HANDLE: $(function)
        return jQuery.makeArray( selector, this );
    };
// Give the init function the jQuery prototype for later instantiation
init.prototype = jQuery.fn;