写得很好的开源项目(用于学习)？

(function(){

var
    // Will speed up references to window, and allows munging its name.
    window = this,
    // Will speed up references to undefined, and allows munging its name.
    undefined,
    // Map over jQuery in case of overwrite
    _jQuery = window.jQuery,
    // Map over the $ in case of overwrite
    _$ = window.$,

    jQuery = window.jQuery = window.$ = function( selector, context ) {
        // The jQuery object is actually just the init constructor 'enhanced'
        return new jQuery.fn.init( selector, context );
    },

    // A simple way to check for HTML strings or ID strings
    // (both of which we optimize for)
    quickExpr = /^[^<]*(<(.|\s)+>)[^>]*$|^#([\w-]+)$/,
    // Is it a simple selector
    isSimple = /^.[^:#\[\.,]*$/;

jQuery.fn = jQuery.prototype = {
    init: function( selector, context ) {
        // Make sure that a selection was provided
        selector = selector || document;

        // Handle $(DOMElement)
        if ( selector.nodeType ) {
            this[0] = selector;
            this.length = 1;
            this.context = selector;
            return this;
        }
        // Handle HTML strings
        if ( typeof selector ==="string" ) {
            // Are we dealing with HTML string or an ID?
            var match = quickExpr.exec( selector );

            // Verify a match, and that no context was specified for #id
            if ( match && (match[1] || !context) ) {

                // HANDLE: $(html) -> $(array)
                if ( match[1] )
                    selector = jQuery.clean( [ match[1] ], context );

                // HANDLE: $("#id")
                else {
                    var elem = document.getElementById( match[3] );

                    // Handle the case where IE and Opera return items
                    // by name instead of ID
                    if ( elem && elem.id != match[3] )
                        return jQuery().find( selector );

...