source: Dev/trunk/src/client/dojo/query.js @ 531

define(["./_base/kernel", "./has", "./dom", "./on", "./_base/array", "./_base/lang", "./selector/_loader", "./selector/_loader!default"],
        function(dojo, has, dom, on, array, lang, loader, defaultEngine){

        "use strict";

        has.add("array-extensible", function(){
                // test to see if we can extend an array (not supported in old IE)
                return lang.delegate([], {length: 1}).length == 1 && !has("bug-for-in-skips-shadowed");
        });
        
        var ap = Array.prototype, aps = ap.slice, apc = ap.concat, forEach = array.forEach;

        var tnl = function(/*Array*/ a, /*dojo/NodeList?*/ parent, /*Function?*/ NodeListCtor){
                // summary:
                //              decorate an array to make it look like a `dojo/NodeList`.
                // a:
                //              Array of nodes to decorate.
                // parent:
                //              An optional parent NodeList that generated the current
                //              list of nodes. Used to call _stash() so the parent NodeList
                //              can be accessed via end() later.
                // NodeListCtor:
                //              An optional constructor function to use for any
                //              new NodeList calls. This allows a certain chain of
                //              NodeList calls to use a different object than dojo/NodeList.
                var nodeList = new (NodeListCtor || this._NodeListCtor || nl)(a);
                return parent ? nodeList._stash(parent) : nodeList;
        };

        var loopBody = function(f, a, o){
                a = [0].concat(aps.call(a, 0));
                o = o || dojo.global;
                return function(node){
                        a[0] = node;
                        return f.apply(o, a);
                };
        };

        // adapters

        var adaptAsForEach = function(f, o){
                // summary:
                //              adapts a single node function to be used in the forEach-type
                //              actions. The initial object is returned from the specialized
                //              function.
                // f: Function
                //              a function to adapt
                // o: Object?
                //              an optional context for f
                return function(){
                        this.forEach(loopBody(f, arguments, o));
                        return this;    // Object
                };
        };

        var adaptAsMap = function(f, o){
                // summary:
                //              adapts a single node function to be used in the map-type
                //              actions. The return is a new array of values, as via `dojo/_base/array.map`
                // f: Function
                //              a function to adapt
                // o: Object?
                //              an optional context for f
                return function(){
                        return this.map(loopBody(f, arguments, o));
                };
        };

        var adaptAsFilter = function(f, o){
                // summary:
                //              adapts a single node function to be used in the filter-type actions
                // f: Function
                //              a function to adapt
                // o: Object?
                //              an optional context for f
                return function(){
                        return this.filter(loopBody(f, arguments, o));
                };
        };

        var adaptWithCondition = function(f, g, o){
                // summary:
                //              adapts a single node function to be used in the map-type
                //              actions, behaves like forEach() or map() depending on arguments
                // f: Function
                //              a function to adapt
                // g: Function
                //              a condition function, if true runs as map(), otherwise runs as forEach()
                // o: Object?
                //              an optional context for f and g
                return function(){
                        var a = arguments, body = loopBody(f, a, o);
                        if(g.call(o || dojo.global, a)){
                                return this.map(body);  // self
                        }
                        this.forEach(body);
                        return this;    // self
                };
        };

        var NodeList = function(array){
                // summary:
                //              Array-like object which adds syntactic
                //              sugar for chaining, common iteration operations, animation, and
                //              node manipulation. NodeLists are most often returned as the
                //              result of dojo/query() calls.
                // description:
                //              NodeList instances provide many utilities that reflect
                //              core Dojo APIs for Array iteration and manipulation, DOM
                //              manipulation, and event handling. Instead of needing to dig up
                //              functions in the dojo package, NodeLists generally make the
                //              full power of Dojo available for DOM manipulation tasks in a
                //              simple, chainable way.
                // example:
                //              create a node list from a node
                //              |       require(["dojo/query", "dojo/dom"
                //              |       ], function(query, dom){
                //              |               query.NodeList(dom.byId("foo"));
                //              |       });
                // example:
                //              get a NodeList from a CSS query and iterate on it
                //              |       require(["dojo/on", "dojo/dom"
                //              |       ], function(on, dom){
                //              |               var l = query(".thinger");
                //              |               l.forEach(function(node, index, nodeList){
                //              |                       console.log(index, node.innerHTML);
                //              |               });
                //              |       });
                // example:
                //              use native and Dojo-provided array methods to manipulate a
                //              NodeList without needing to use dojo.* functions explicitly:
                //              |       require(["dojo/query", "dojo/dom-construct", "dojo/dom"
                //              |       ], function(query, domConstruct, dom){
                //              |               var l = query(".thinger");
                //              |               // since NodeLists are real arrays, they have a length
                //              |               // property that is both readable and writable and
                //              |               // push/pop/shift/unshift methods
                //              |               console.log(l.length);
                //              |               l.push(domConstruct.create("span"));
                //              |
                //              |               // dojo's normalized array methods work too:
                //              |               console.log( l.indexOf(dom.byId("foo")) );
                //              |               // ...including the special "function as string" shorthand
                //              |               console.log( l.every("item.nodeType == 1") );
                //              |
                //              |               // NodeLists can be [..] indexed, or you can use the at()
                //              |               // function to get specific items wrapped in a new NodeList:
                //              |               var node = l[3]; // the 4th element
                //              |               var newList = l.at(1, 3); // the 2nd and 4th elements
                //              |       });
                // example:
                //              chainability is a key advantage of NodeLists:
                //              |       require(["dojo/query", "dojo/NodeList-dom"
                //              |       ], function(query){
                //              |               query(".thinger")
                //              |                       .onclick(function(e){ /* ... */ })
                //              |                       .at(1, 3, 8) // get a subset
                //              |                               .style("padding", "5px")
                //              |                               .forEach(console.log);
                //              |       });

                var isNew = this instanceof nl && has("array-extensible");
                if(typeof array == "number"){
                        array = Array(array);
                }
                var nodeArray = (array && "length" in array) ? array : arguments;
                if(isNew || !nodeArray.sort){
                        // make sure it's a real array before we pass it on to be wrapped 
                        var target = isNew ? this : [],
                                l = target.length = nodeArray.length;
                        for(var i = 0; i < l; i++){
                                target[i] = nodeArray[i];
                        }
                        if(isNew){
                                // called with new operator, this means we are going to use this instance and push
                                // the nodes on to it. This is usually much faster since the NodeList properties
                                //      don't need to be copied (unless the list of nodes is extremely large).
                                return target;
                        }
                        nodeArray = target;
                }
                // called without new operator, use a real array and copy prototype properties,
                // this is slower and exists for back-compat. Should be removed in 2.0.
                lang._mixin(nodeArray, nlp);
                nodeArray._NodeListCtor = function(array){
                        // call without new operator to preserve back-compat behavior
                        return nl(array);
                };
                return nodeArray;
        };
        
        var nl = NodeList, nlp = nl.prototype = 
                has("array-extensible") ? [] : {};// extend an array if it is extensible

        // expose adapters and the wrapper as private functions

        nl._wrap = nlp._wrap = tnl;
        nl._adaptAsMap = adaptAsMap;
        nl._adaptAsForEach = adaptAsForEach;
        nl._adaptAsFilter  = adaptAsFilter;
        nl._adaptWithCondition = adaptWithCondition;

        // mass assignment

        // add array redirectors
        forEach(["slice", "splice"], function(name){
                var f = ap[name];
                //Use a copy of the this array via this.slice() to allow .end() to work right in the splice case.
                // CANNOT apply ._stash()/end() to splice since it currently modifies
                // the existing this array -- it would break backward compatibility if we copy the array before
                // the splice so that we can use .end(). So only doing the stash option to this._wrap for slice.
                nlp[name] = function(){ return this._wrap(f.apply(this, arguments), name == "slice" ? this : null); };
        });
        // concat should be here but some browsers with native NodeList have problems with it

        // add array.js redirectors
        forEach(["indexOf", "lastIndexOf", "every", "some"], function(name){
                var f = array[name];
                nlp[name] = function(){ return f.apply(dojo, [this].concat(aps.call(arguments, 0))); };
        });

        lang.extend(NodeList, {
                // copy the constructors
                constructor: nl,
                _NodeListCtor: nl,
                toString: function(){
                        // Array.prototype.toString can't be applied to objects, so we use join
                        return this.join(",");
                },
                _stash: function(parent){
                        // summary:
                        //              private function to hold to a parent NodeList. end() to return the parent NodeList.
                        //
                        // example:
                        //              How to make a `dojo/NodeList` method that only returns the third node in
                        //              the dojo/NodeList but allows access to the original NodeList by using this._stash:
                        //      |       require(["dojo/query", "dojo/_base/lang", "dojo/NodeList", "dojo/NodeList-dom"
                        //      |       ], function(query, lang){
                        //      |               lang.extend(NodeList, {
                        //      |                       third: function(){
                        //      |                               var newNodeList = NodeList(this[2]);
                        //      |                               return newNodeList._stash(this);
                        //      |                       }
                        //      |               });
                        //      |               // then see how _stash applies a sub-list, to be .end()'ed out of
                        //      |               query(".foo")
                        //      |                       .third()
                        //      |                               .addClass("thirdFoo")
                        //      |                       .end()
                        //      |                       // access to the orig .foo list
                        //      |                       .removeClass("foo")
                        //      |       });
                        //
                        this._parent = parent;
                        return this; // dojo/NodeList
                },

                on: function(eventName, listener){
                        // summary:
                        //              Listen for events on the nodes in the NodeList. Basic usage is:
                        //
                        // example:
                        //              |       require(["dojo/query"
                        //              |       ], function(query){
                        //              |               query(".my-class").on("click", listener);
                        //                      This supports event delegation by using selectors as the first argument with the event names as
                        //                      pseudo selectors. For example:
                        //              |               query("#my-list").on("li:click", listener);
                        //                      This will listen for click events within `<li>` elements that are inside the `#my-list` element.
                        //                      Because on supports CSS selector syntax, we can use comma-delimited events as well:
                        //              |               query("#my-list").on("li button:mouseover, li:click", listener);
                        //              |       });
                        var handles = this.map(function(node){
                                return on(node, eventName, listener); // TODO: apply to the NodeList so the same selector engine is used for matches
                        });
                        handles.remove = function(){
                                for(var i = 0; i < handles.length; i++){
                                        handles[i].remove();
                                }
                        };
                        return handles;
                },

                end: function(){
                        // summary:
                        //              Ends use of the current `NodeList` by returning the previous NodeList
                        //              that generated the current NodeList.
                        // description:
                        //              Returns the `NodeList` that generated the current `NodeList`. If there
                        //              is no parent NodeList, an empty NodeList is returned.
                        // example:
                        //      |       require(["dojo/query", "dojo/NodeList-dom"
                        //      |       ], function(query){
                        //      |               query("a")
                        //      |                       .filter(".disabled")
                        //      |                               // operate on the anchors that only have a disabled class
                        //      |                               .style("color", "grey")
                        //      |                       .end()
                        //      |                       // jump back to the list of anchors
                        //      |                       .style(...)
                        //      |       });
                        //
                        if(this._parent){
                                return this._parent;
                        }else{
                                //Just return empty list.
                                return new this._NodeListCtor(0);
                        }
                },

                // http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Reference:Global_Objects:Array#Methods

                // FIXME: handle return values for #3244
                //              http://trac.dojotoolkit.org/ticket/3244

                // FIXME:
                //              need to wrap or implement:
                //                      join (perhaps w/ innerHTML/outerHTML overload for toString() of items?)
                //                      reduce
                //                      reduceRight

                /*=====
                slice: function(begin, end){
                        // summary:
                        //              Returns a new NodeList, maintaining this one in place
                        // description:
                        //              This method behaves exactly like the Array.slice method
                        //              with the caveat that it returns a `dojo/NodeList` and not a
                        //              raw Array. For more details, see Mozilla's [slice
                        //              documentation](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/slice)
                        // begin: Integer
                        //              Can be a positive or negative integer, with positive
                        //              integers noting the offset to begin at, and negative
                        //              integers denoting an offset from the end (i.e., to the left
                        //              of the end)
                        // end: Integer?
                        //              Optional parameter to describe what position relative to
                        //              the NodeList's zero index to end the slice at. Like begin,
                        //              can be positive or negative.
                        return this._wrap(a.slice.apply(this, arguments));
                },

                splice: function(index, howmany, item){
                        // summary:
                        //              Returns a new NodeList, manipulating this NodeList based on
                        //              the arguments passed, potentially splicing in new elements
                        //              at an offset, optionally deleting elements
                        // description:
                        //              This method behaves exactly like the Array.splice method
                        //              with the caveat that it returns a `dojo/NodeList` and not a
                        //              raw Array. For more details, see Mozilla's [splice
                        //              documentation](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/splice)
                        //              For backwards compatibility, calling .end() on the spliced NodeList
                        //              does not return the original NodeList -- splice alters the NodeList in place.
                        // index: Integer
                        //              begin can be a positive or negative integer, with positive
                        //              integers noting the offset to begin at, and negative
                        //              integers denoting an offset from the end (i.e., to the left
                        //              of the end)
                        // howmany: Integer?
                        //              Optional parameter to describe what position relative to
                        //              the NodeList's zero index to end the slice at. Like begin,
                        //              can be positive or negative.
                        // item: Object...?
                        //              Any number of optional parameters may be passed in to be
                        //              spliced into the NodeList
                        return this._wrap(a.splice.apply(this, arguments));     // dojo/NodeList
                },

                indexOf: function(value, fromIndex){
                        // summary:
                        //              see `dojo/_base/array.indexOf()`. The primary difference is that the acted-on
                        //              array is implicitly this NodeList
                        // value: Object
                        //              The value to search for.
                        // fromIndex: Integer?
                        //              The location to start searching from. Optional. Defaults to 0.
                        // description:
                        //              For more details on the behavior of indexOf, see Mozilla's
                        //              [indexOf
                        //              docs](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/indexOf)
                        // returns:
                        //              Positive Integer or 0 for a match, -1 of not found.
                        return d.indexOf(this, value, fromIndex); // Integer
                },

                lastIndexOf: function(value, fromIndex){
                        // summary:
                        //              see `dojo/_base/array.lastIndexOf()`. The primary difference is that the
                        //              acted-on array is implicitly this NodeList
                        // description:
                        //              For more details on the behavior of lastIndexOf, see
                        //              Mozilla's [lastIndexOf
                        //              docs](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/lastIndexOf)
                        // value: Object
                        //              The value to search for.
                        // fromIndex: Integer?
                        //              The location to start searching from. Optional. Defaults to 0.
                        // returns:
                        //              Positive Integer or 0 for a match, -1 of not found.
                        return d.lastIndexOf(this, value, fromIndex); // Integer
                },

                every: function(callback, thisObject){
                        // summary:
                        //              see `dojo/_base/array.every()` and the [Array.every
                        //              docs](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/every).
                        //              Takes the same structure of arguments and returns as
                        //              dojo/_base/array.every() with the caveat that the passed array is
                        //              implicitly this NodeList
                        // callback: Function
                        //              the callback
                        // thisObject: Object?
                        //              the context
                        return d.every(this, callback, thisObject); // Boolean
                },

                some: function(callback, thisObject){
                        // summary:
                        //              Takes the same structure of arguments and returns as
                        //              `dojo/_base/array.some()` with the caveat that the passed array is
                        //              implicitly this NodeList.  See `dojo/_base/array.some()` and Mozilla's
                        //              [Array.some
                        //              documentation](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/some).
                        // callback: Function
                        //              the callback
                        // thisObject: Object?
                        //              the context
                        return d.some(this, callback, thisObject); // Boolean
                },
                =====*/

                concat: function(item){
                        // summary:
                        //              Returns a new NodeList comprised of items in this NodeList
                        //              as well as items passed in as parameters
                        // description:
                        //              This method behaves exactly like the Array.concat method
                        //              with the caveat that it returns a `NodeList` and not a
                        //              raw Array. For more details, see the [Array.concat
                        //              docs](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/concat)
                        // item: Object?
                        //              Any number of optional parameters may be passed in to be
                        //              spliced into the NodeList

                        //return this._wrap(apc.apply(this, arguments));
                        // the line above won't work for the native NodeList, or for Dojo NodeLists either :-(

                        // implementation notes:
                        // Array.concat() doesn't recognize native NodeLists or Dojo NodeLists
                        // as arrays, and so does not inline them into a unioned array, but
                        // appends them as single entities. Both the original NodeList and the
                        // items passed in as parameters must be converted to raw Arrays
                        // and then the concatenation result may be re-_wrap()ed as a Dojo NodeList.

                        var t = aps.call(this, 0),
                                m = array.map(arguments, function(a){
                                        return aps.call(a, 0);
                                });
                        return this._wrap(apc.apply(t, m), this);       // dojo/NodeList
                },

                map: function(/*Function*/ func, /*Function?*/ obj){
                        // summary:
                        //              see `dojo/_base/array.map()`. The primary difference is that the acted-on
                        //              array is implicitly this NodeList and the return is a
                        //              NodeList (a subclass of Array)
                        return this._wrap(array.map(this, func, obj), this); // dojo/NodeList
                },

                forEach: function(callback, thisObj){
                        // summary:
                        //              see `dojo/_base/array.forEach()`. The primary difference is that the acted-on
                        //              array is implicitly this NodeList. If you want the option to break out
                        //              of the forEach loop, use every() or some() instead.
                        forEach(this, callback, thisObj);
                        // non-standard return to allow easier chaining
                        return this; // dojo/NodeList
                },
                filter: function(/*String|Function*/ filter){
                        // summary:
                        //              "masks" the built-in javascript filter() method (supported
                        //              in Dojo via `dojo/_base/array.filter`) to support passing a simple
                        //              string filter in addition to supporting filtering function
                        //              objects.
                        // filter:
                        //              If a string, a CSS rule like ".thinger" or "div > span".
                        // example:
                        //              "regular" JS filter syntax as exposed in `dojo/_base/array.filter`:
                        //              |       require(["dojo/query", "dojo/NodeList-dom"
                        //              |       ], function(query){
                        //              |               query("*").filter(function(item){
                        //              |                       // highlight every paragraph
                        //              |                       return (item.nodeName == "p");
                        //              |               }).style("backgroundColor", "yellow");
                        //              |       });
                        // example:
                        //              the same filtering using a CSS selector
                        //              |       require(["dojo/query", "dojo/NodeList-dom"
                        //              |       ], function(query){
                        //              |               query("*").filter("p").styles("backgroundColor", "yellow");
                        //              |       });

                        var a = arguments, items = this, start = 0;
                        if(typeof filter == "string"){ // inline'd type check
                                items = query._filterResult(this, a[0]);
                                if(a.length == 1){
                                        // if we only got a string query, pass back the filtered results
                                        return items._stash(this); // dojo/NodeList
                                }
                                // if we got a callback, run it over the filtered items
                                start = 1;
                        }
                        return this._wrap(array.filter(items, a[start], a[start + 1]), this);   // dojo/NodeList
                },
                instantiate: function(/*String|Object*/ declaredClass, /*Object?*/ properties){
                        // summary:
                        //              Create a new instance of a specified class, using the
                        //              specified properties and each node in the NodeList as a
                        //              srcNodeRef.
                        // example:
                        //              Grabs all buttons in the page and converts them to dijit/form/Button's.
                        //      |       var buttons = query("button").instantiate(Button, {showLabel: true});
                        var c = lang.isFunction(declaredClass) ? declaredClass : lang.getObject(declaredClass);
                        properties = properties || {};
                        return this.forEach(function(node){
                                new c(properties, node);
                        });     // dojo/NodeList
                },
                at: function(/*===== index =====*/){
                        // summary:
                        //              Returns a new NodeList comprised of items in this NodeList
                        //              at the given index or indices.
                        //
                        // index: Integer...
                        //              One or more 0-based indices of items in the current
                        //              NodeList. A negative index will start at the end of the
                        //              list and go backwards.
                        //
                        // example:
                        //      Shorten the list to the first, second, and third elements
                        //      |       require(["dojo/query"
                        //      |       ], function(query){
                        //      |               query("a").at(0, 1, 2).forEach(fn);
                        //      |       });
                        //
                        // example:
                        //      Retrieve the first and last elements of a unordered list:
                        //      |       require(["dojo/query"
                        //      |       ], function(query){
                        //      |               query("ul > li").at(0, -1).forEach(cb);
                        //      |       });
                        //
                        // example:
                        //      Do something for the first element only, but end() out back to
                        //      the original list and continue chaining:
                        //      |       require(["dojo/query"
                        //      |       ], function(query){
                        //      |               query("a").at(0).onclick(fn).end().forEach(function(n){
                        //      |                       console.log(n); // all anchors on the page.
                        //      |       })
                        //      |       });

                        var t = new this._NodeListCtor(0);
                        forEach(arguments, function(i){
                                if(i < 0){ i = this.length + i; }
                                if(this[i]){ t.push(this[i]); }
                        }, this);
                        return t._stash(this); // dojo/NodeList
                }
        });

        function queryForEngine(engine, NodeList){
                var query = function(/*String*/ query, /*String|DOMNode?*/ root){
                        // summary:
                        //              Returns nodes which match the given CSS selector, searching the
                        //              entire document by default but optionally taking a node to scope
                        //              the search by. Returns an instance of NodeList.
                        if(typeof root == "string"){
                                root = dom.byId(root);
                                if(!root){
                                        return new NodeList([]);
                                }
                        }
                        var results = typeof query == "string" ? engine(query, root) : query ? (query.end && query.on) ? query : [query] : [];
                        if(results.end && results.on){
                                // already wrapped
                                return results;
                        }
                        return new NodeList(results);
                };
                query.matches = engine.match || function(node, selector, root){
                        // summary:
                        //              Test to see if a node matches a selector
                        return query.filter([node], selector, root).length > 0;
                };
                // the engine provides a filtering function, use it to for matching
                query.filter = engine.filter || function(nodes, selector, root){
                        // summary:
                        //              Filters an array of nodes. Note that this does not guarantee to return a NodeList, just an array.
                        return query(selector, root).filter(function(node){
                                return array.indexOf(nodes, node) > -1;
                        });
                };
                if(typeof engine != "function"){
                        var search = engine.search;
                        engine = function(selector, root){
                                // Slick does it backwards (or everyone else does it backwards, probably the latter)
                                return search(root || document, selector);
                        };
                }
                return query;
        }
        var query = queryForEngine(defaultEngine, NodeList);
        /*=====
        query = function(selector, context){
                // summary:
                //              This modules provides DOM querying functionality. The module export is a function
                //              that can be used to query for DOM nodes by CSS selector and returns a NodeList
                //              representing the matching nodes.
                // selector: String
                //              A CSS selector to search for.
                // context: String|DomNode?
                //              An optional context to limit the searching scope. Only nodes under `context` will be
                //              scanned.
                // example:
                //              add an onclick handler to every submit button in the document
                //              which causes the form to be sent via Ajax instead:
                //      |       require(["dojo/query", "dojo/request", "dojo/dom-form", "dojo/dom-construct", "dojo/dom-style"
                //      |       ], function(query, request, domForm, domConstruct, domStyle){
                //      |               query("input[type='submit']").on("click", function(e){
                //      |                       e.preventDefault(); // prevent sending the form
                //      |                       var btn = e.target;
                //      |                       request.post("http://example.com/", {
                //      |                               data: domForm.toObject(btn.form)
                //      |                       }).then(function(response){
                //      |                               // replace the form with the response
                //      |                               domConstruct.create(div, {innerHTML: response}, btn.form, "after");
                //      |                               domStyle.set(btn.form, "display", "none");
                //      |                       });
                //      |               });
                //      |       });
                //
                // description:
                //              dojo/query is responsible for loading the appropriate query engine and wrapping
                //              its results with a `NodeList`. You can use dojo/query with a specific selector engine
                //              by using it as a plugin. For example, if you installed the sizzle package, you could
                //              use it as the selector engine with:
                //              |       require(["dojo/query!sizzle"], function(query){
                //              |               query("div")...
                //
                //              The id after the ! can be a module id of the selector engine or one of the following values:
                //
                //              - acme: This is the default engine used by Dojo base, and will ensure that the full
                //              Acme engine is always loaded.
                //
                //              - css2: If the browser has a native selector engine, this will be used, otherwise a
                //              very minimal lightweight selector engine will be loaded that can do simple CSS2 selectors
                //              (by #id, .class, tag, and [name=value] attributes, with standard child or descendant (>)
                //              operators) and nothing more.
                //
                //              - css2.1: If the browser has a native selector engine, this will be used, otherwise the
                //              full Acme engine will be loaded.
                //
                //              - css3: If the browser has a native selector engine with support for CSS3 pseudo
                //              selectors (most modern browsers except IE8), this will be used, otherwise the
                //              full Acme engine will be loaded.
                //
                //              - Or the module id of a selector engine can be used to explicitly choose the selector engine
                //
                //              For example, if you are using CSS3 pseudo selectors in module, you can specify that
                //              you will need support them with:
                //              |       require(["dojo/query!css3"], function(query){
                //              |               query('#t > h3:nth-child(odd)')...
                //
                //              You can also choose the selector engine/load configuration by setting the query-selector:
                //              For example:
                //              |       <script data-dojo-config="query-selector:'css3'" src="dojo.js"></script>
                //
                return new NodeList(); // dojo/NodeList
         };
         =====*/

        // the query that is returned from this module is slightly different than dojo.query,
        // because dojo.query has to maintain backwards compatibility with returning a
        // true array which has performance problems. The query returned from the module
        // does not use true arrays, but rather inherits from Array, making it much faster to
        // instantiate.
        dojo.query = queryForEngine(defaultEngine, function(array){
                // call it without the new operator to invoke the back-compat behavior that returns a true array
                return NodeList(array); // dojo/NodeList
        });

        query.load = function(id, parentRequire, loaded){
                // summary:
                //              can be used as AMD plugin to conditionally load new query engine
                // example:
                //      |       require(["dojo/query!custom"], function(qsa){
                //      |               // loaded selector/custom.js as engine
                //      |               qsa("#foobar").forEach(...);
                //      |       });
                loader.load(id, parentRequire, function(engine){
                        loaded(queryForEngine(engine, NodeList));
                });
        };

        dojo._filterQueryResult = query._filterResult = function(nodes, selector, root){
                return new NodeList(query.filter(nodes, selector, root));
        };
        dojo.NodeList = query.NodeList = NodeList;
        return query;
});