source: Dev/trunk/src/client/dojo/request/script.js

define([
        'module',
        './watch',
        './util',
        '../_base/array',
        '../_base/lang',
        '../on',
        '../dom',
        '../dom-construct',
        '../has',
        '../_base/window'/*=====,
        '../request',
        '../_base/declare' =====*/
], function(module, watch, util, array, lang, on, dom, domConstruct, has, win/*=====, request, declare =====*/){
        has.add('script-readystatechange', function(global, document){
                var script = document.createElement('script');
                return typeof script['onreadystatechange'] !== 'undefined' &&
                        (typeof global['opera'] === 'undefined' || global['opera'].toString() !== '[object Opera]');
        });

        var mid = module.id.replace(/[\/\.\-]/g, '_'),
                counter = 0,
                loadEvent = has('script-readystatechange') ? 'readystatechange' : 'load',
                readyRegExp = /complete|loaded/,
                callbacks = this[mid + '_callbacks'] = {},
                deadScripts = [];

        function attach(id, url, frameDoc){
                var doc = (frameDoc || win.doc),
                        element = doc.createElement('script');

                element.type = 'text/javascript';
                element.src = url;
                element.id = id;
                element.async = true;
                element.charset = 'utf-8';

                return doc.getElementsByTagName('head')[0].appendChild(element);
        }

        function remove(id, frameDoc, cleanup){
                domConstruct.destroy(dom.byId(id, frameDoc));

                if(callbacks[id]){
                        if(cleanup){
                                // set callback to a function that deletes itself so requests that
                                // are in-flight don't error out when returning and also
                                // clean up after themselves
                                callbacks[id] = function(){
                                        delete callbacks[id];
                                };
                        }else{
                                delete callbacks[id];
                        }
                }
        }

        function _addDeadScript(dfd){
                // Be sure to check ioArgs because it can dynamically change in the dojox/io plugins.
                // See http://bugs.dojotoolkit.org/ticket/15890.
                var options = dfd.response.options,
                        frameDoc = options.ioArgs ? options.ioArgs.frameDoc : options.frameDoc;

                deadScripts.push({ id: dfd.id, frameDoc: frameDoc });

                if(options.ioArgs){
                        options.ioArgs.frameDoc = null;
                }
                options.frameDoc = null;
        }

        function canceler(dfd, response){
                if(dfd.canDelete){
                        //For timeouts and cancels, remove the script element immediately to
                        //avoid a response from it coming back later and causing trouble.
                        script._remove(dfd.id, response.options.frameDoc, true);
                }
        }
        function isValid(response){
                //Do script cleanup here. We wait for one inflight pass
                //to make sure we don't get any weird things by trying to remove a script
                //tag that is part of the call chain (IE 6 has been known to
                //crash in that case).
                if(deadScripts && deadScripts.length){
                        array.forEach(deadScripts, function(_script){
                                script._remove(_script.id, _script.frameDoc);
                                _script.frameDoc = null;
                        });
                        deadScripts = [];
                }

                return response.options.jsonp ? !response.data : true;
        }
        function isReadyScript(response){
                return !!this.scriptLoaded;
        }
        function isReadyCheckString(response){
                var checkString = response.options.checkString;

                return checkString && eval('typeof(' + checkString + ') !== "undefined"');
        }
        function handleResponse(response, error){
                if(this.canDelete){
                        _addDeadScript(this);
                }
                if(error){
                        this.reject(error);
                }else{
                        this.resolve(response);
                }
        }

        function script(url, options, returnDeferred){
                var response = util.parseArgs(url, util.deepCopy({}, options));
                url = response.url;
                options = response.options;

                var dfd = util.deferred(
                        response,
                        canceler,
                        isValid,
                        options.jsonp ? null : (options.checkString ? isReadyCheckString : isReadyScript),
                        handleResponse
                );

                lang.mixin(dfd, {
                        id: mid + (counter++),
                        canDelete: false
                });

                if(options.jsonp){
                        var queryParameter = new RegExp('[?&]' + options.jsonp + '=');
                        if(!queryParameter.test(url)){
                                url += (~url.indexOf('?') ? '&' : '?') +
                                        options.jsonp + '=' +
                                        (options.frameDoc ? 'parent.' : '') +
                                        mid + '_callbacks.' + dfd.id;
                        }

                        dfd.canDelete = true;
                        callbacks[dfd.id] = function(json){
                                response.data = json;
                                dfd.handleResponse(response);
                        };
                }

                if(util.notify){
                        util.notify.emit('send', response, dfd.promise.cancel);
                }

                if(!options.canAttach || options.canAttach(dfd)){
                        var node = script._attach(dfd.id, url, options.frameDoc);

                        if(!options.jsonp && !options.checkString){
                                var handle = on(node, loadEvent, function(evt){
                                        if(evt.type === 'load' || readyRegExp.test(node.readyState)){
                                                handle.remove();
                                                dfd.scriptLoaded = evt;
                                        }
                                });
                        }
                }

                watch(dfd);

                return returnDeferred ? dfd : dfd.promise;
        }
        script.get = script;
        /*=====
        script = function(url, options){
                // summary:
                //              Sends a request using a script element with the given URL and options.
                // url: String
                //              URL to request
                // options: dojo/request/script.__Options?
                //              Options for the request.
                // returns: dojo/request.__Promise
        };
        script.__BaseOptions = declare(request.__BaseOptions, {
                // jsonp: String?
                //              The URL parameter name that indicates the JSONP callback string.
                //              For instance, when using Yahoo JSONP calls it is normally,
                //              jsonp: "callback". For AOL JSONP calls it is normally
                //              jsonp: "c".
                // checkString: String?
                //              A string of JavaScript that when evaluated like so:
                //              "typeof(" + checkString + ") != 'undefined'"
                //              being true means that the script fetched has been loaded.
                //              Do not use this if doing a JSONP type of call (use `jsonp` instead).
                // frameDoc: Document?
                //              The Document object of a child iframe. If this is passed in, the script
                //              will be attached to that document. This can be helpful in some comet long-polling
                //              scenarios with Firefox and Opera.
        });
        script.__MethodOptions = declare(null, {
                // method: String?
                //              This option is ignored. All requests using this transport are
                //              GET requests.
        });
        script.__Options = declare([script.__BaseOptions, script.__MethodOptions]);

        script.get = function(url, options){
                // summary:
                //              Send an HTTP GET request using a script element with the given URL and options.
                // url: String
                //              URL to request
                // options: dojo/request/script.__BaseOptions?
                //              Options for the request.
                // returns: dojo/request.__Promise
        };
        =====*/

        // TODO: Remove in 2.0
        script._attach = attach;
        script._remove = remove;
        script._callbacksProperty = mid + '_callbacks';

        return script;
});