for jquery learn

base.js

(function(exports, undefined){
    //redefine document
    var document = exports.document;
    //namse space
    var BASE = (function(){
        

        // base obj
        var BASE = function(selector, context){
            return new BASE.fn.init();
        }

        BASE.fn = BASE.prototype = {
            constructor: BASE,


        };

        //leave context to be null
        init = BASE.fn.init = function(selector, context){
            var match, elem;
            var elems;
            //handle $('')
            if(!selector) return this;
            else if(typeof selector == 'string'){
                selector = selector.trim();

                quickExpr = /^[\w-]*$/;

                var mayID = selector[0] == '#',
                    mayClass = !mayID && selector[0] == '.',
                    nameOnly = mayID || mayClass ? selector.slice(1) : selector,
                    isSimple = quickExpr.test(nameOnly);
                if(isSimple){
                    //handle $('#ID')
                    if(mayID){
                        elem = document.getElementById(nameOnly);

                        if(elem && elem.parentNode){
                            this.length = 1;
                            //use index 0 to store dom obj
                            this[0] = elem;  
                        }

                        this.context = document;
                        return this;
                    }else if(mayClass){
                        //handle $('.CLASS') no context
                        if(document.getElementsByClassName){
                            elems = document.getElementsByClassName(nameOnly);
                        }
                        
                        this[0] = elems;  
                        return this;

                    }else{
                        elems = document.getElementsByTagName(nameOnly);
                    }
                }else{
                    //try complex selector
                    elems = document.querySelectorAll(selector);
                }
                
            }
        };
        init.prototype = BASE.fn;


        return BASE;

    })();

    
    //may confilct?
    //exports.BASE = exports.$ = BASE;
    exports.BASE = BASE;
    exports.$ === undefined && (exports.$ = BASE);

})(window);