get.js

这是YUI的源码及相关示例。里面有很多很炫的Javascript效果。

/*
Copyright (c) 2008, Yahoo! Inc. All rights reserved.
Code licensed under the BSD License:
http://developer.yahoo.net/yui/license.txt
version: 2.6.0
*/
/**
 * Provides a mechanism to fetch remote resources and
 * insert them into a document
 * @module get
 * @requires yahoo
 */

/**
 * Fetches and inserts one or more script or link nodes into the document 
 * @namespace YAHOO.util
 * @class YAHOO.util.Get
 */
YAHOO.util.Get = function() {

    /**
     * hash of queues to manage multiple requests
     * @property queues
     * @private
     */
    var queues={}, 
        
    /**
     * queue index used to generate transaction ids
     * @property qidx
     * @type int
     * @private
     */
        qidx=0, 
        
    /**
     * node index used to generate unique node ids
     * @property nidx
     * @type int
     * @private
     */
        nidx=0, 

        // ridx=0,

        // sandboxFrame=null,

    /**
     * interal property used to prevent multiple simultaneous purge 
     * processes
     * @property purging
     * @type boolean
     * @private
     */
        purging=false,

        ua=YAHOO.env.ua, 
        
        lang=YAHOO.lang;
    
    /** 
     * Generates an HTML element, this is not appended to a document
     * @method _node
     * @param type {string} the type of element
     * @param attr {string} the attributes
     * @param win {Window} optional window to create the element in
     * @return {HTMLElement} the generated node
     * @private
     */
    var _node = function(type, attr, win) {
        var w = win || window, d=w.document, n=d.createElement(type);

        for (var i in attr) {
            if (attr[i] && YAHOO.lang.hasOwnProperty(attr, i)) {
                n.setAttribute(i, attr[i]);
            }
        }

        return n;
    };

    /**
     * Generates a link node
     * @method _linkNode
     * @param url {string} the url for the css file
     * @param win {Window} optional window to create the node in
     * @return {HTMLElement} the generated node
     * @private
     */
    var _linkNode = function(url, win, charset) {
        var c = charset || "utf-8";
        return _node("link", {
                "id":      "yui__dyn_" + (nidx++),
                "type":    "text/css",
                "charset": c,
                "rel":     "stylesheet",
                "href":    url
            }, win);
    };

    /**
     * Generates a script node
     * @method _scriptNode
     * @param url {string} the url for the script file
     * @param win {Window} optional window to create the node in
     * @return {HTMLElement} the generated node
     * @private
     */
    var _scriptNode = function(url, win, charset) {
        var c = charset || "utf-8";
        return _node("script", {
                "id":      "yui__dyn_" + (nidx++),
                "type":    "text/javascript",
                "charset": c,
                "src":     url
            }, win);
    };

    /**
     * Returns the data payload for callback functions
     * @method _returnData
     * @private
     */
    var _returnData = function(q, msg) {
        return {
                tId: q.tId,
                win: q.win,
                data: q.data,
                nodes: q.nodes,
                msg: msg,
                purge: function() {
                    _purge(this.tId);
                }
            };
    };

    var _get = function(nId, tId) {
        var q = queues[tId],
            n = (lang.isString(nId)) ? q.win.document.getElementById(nId) : nId;
        if (!n) {
            _fail(tId, "target node not found: " + nId);
        }

        return n;
    };

    /*
     * The request failed, execute fail handler with whatever
     * was accomplished.  There isn't a failure case at the
     * moment unless you count aborted transactions
     * @method _fail
     * @param id {string} the id of the request
     * @private
     */
    var _fail = function(id, msg) {
        var q = queues[id];
        // execute failure callback
        if (q.onFailure) {
            var sc=q.scope || q.win;
            q.onFailure.call(sc, _returnData(q, msg));
        }
    };

    /**
     * The request is complete, so executing the requester's callback
     * @method _finish
     * @param id {string} the id of the request
     * @private
     */
    var _finish = function(id) {
        var q = queues[id];
        q.finished = true;

        if (q.aborted) {
            var msg = "transaction " + id + " was aborted";
            _fail(id, msg);
            return;
        }

        // execute success callback
        if (q.onSuccess) {
            var sc=q.scope || q.win;
            q.onSuccess.call(sc, _returnData(q));
        }
    };

    /**
     * Timeout detected
     * @method _timeout
     * @param id {string} the id of the request
     * @private
     */
    var _timeout = function(id) {
        var q = queues[id];
        if (q.onTimeout) {
            var sc=q.context || q;
            q.onTimeout.call(sc, _returnData(q));
        }
    };

    /**
     * Loads the next item for a given request
     * @method _next
     * @param id {string} the id of the request
     * @param loaded {string} the url that was just loaded, if any
     * @private
     */
    var _next = function(id, loaded) {
        var q = queues[id];

        if (q.timer) {
            // Y.log('cancel timer');
            q.timer.cancel();
        }

        if (q.aborted) {
            var msg = "transaction " + id + " was aborted";
            _fail(id, msg);
            return;
        }

        if (loaded) {
            q.url.shift(); 
            if (q.varName) {
                q.varName.shift(); 
            }
        } else {
            // This is the first pass: make sure the url is an array
            q.url = (lang.isString(q.url)) ? [q.url] : q.url;
            if (q.varName) {
                q.varName = (lang.isString(q.varName)) ? [q.varName] : q.varName;
            }
        }

        var w=q.win, d=w.document, h=d.getElementsByTagName("head")[0], n;

        if (q.url.length === 0) {
            // Safari 2.x workaround - There is no way to know when 
            // a script is ready in versions of Safari prior to 3.x.
            // Adding an extra node reduces the problem, but doesn't
            // eliminate it completely because the browser executes
            // them asynchronously. 
            if (q.type === "script" && ua.webkit && ua.webkit < 420 && 
                    !q.finalpass && !q.varName) {
                // Add another script node.  This does not guarantee that the
                // scripts will execute in order, but it does appear to fix the
                // problem on fast connections more effectively than using an
                // arbitrary timeout.  It is possible that the browser does
                // block subsequent script execution in this case for a limited
                // time.
                var extra = _scriptNode(null, q.win, q.charset);
                extra.innerHTML='YAHOO.util.Get._finalize("' + id + '");';
                q.nodes.push(extra); h.appendChild(extra);

            } else {
                _finish(id);
            }

            return;
        } 


        var url = q.url[0];

        // if the url is undefined, this is probably a trailing comma problem in IE
        if (!url) {
            q.url.shift(); 
            return _next(id);
        }


        if (q.timeout) {
            // Y.log('create timer');
            q.timer = lang.later(q.timeout, q, _timeout, id);
        }

        if (q.type === "script") {
            n = _scriptNode(url, w, q.charset);
        } else {
            n = _linkNode(url, w, q.charset);
        }

        // track this node's load progress
        _track(q.type, n, id, url, w, q.url.length);

        // add the node to the queue so we can return it to the user supplied callback
        q.nodes.push(n);

        // add it to the head or insert it before 'insertBefore'
        if (q.insertBefore) {
            var s = _get(q.insertBefore, id);
            if (s) {
                s.parentNode.insertBefore(n, s);
            }
        } else {
            h.appendChild(n);
        }
        

        // FireFox does not support the onload event for link nodes, so there is
        // no way to make the css requests synchronous. This means that the css 
        // rules in multiple files could be applied out of order in this browser
        // if a later request returns before an earlier one.  Safari too.
        if ((ua.webkit || ua.gecko) && q.type === "css") {
            _next(id, url);
        }
    };

    /**
     * Removes processed queues and corresponding nodes
     * @method _autoPurge
     * @private
     */
    var _autoPurge = function() {

        if (purging) {
            return;
        }

        purging = true;
        for (var i in queues) {
            var q = queues[i];
            if (q.autopurge && q.finished) {
                _purge(q.tId);
                delete queues[i];
            }
        }

        purging = false;
    };

    /**
     * Removes the nodes for the specified queue
     * @method _purge
     * @private
     */
    var _purge = function(tId) {
        var q=queues[tId];
        if (q) {
            var n=q.nodes, l=n.length, d=q.win.document, 
                h=d.getElementsByTagName("head")[0];

            if (q.insertBefore) {
                var s = _get(q.insertBefore, tId);
                if (s) {
                    h = s.parentNode;
                }
            }

            for (var i=0; i<l; i=i+1) {
                h.removeChild(n[i]);
            }

            q.nodes = [];
        }
    };

    /**
     * Saves the state for the request and begins loading
     * the requested urls
     * @method queue
     * @param type {string} the type of node to insert
     * @param url {string} the url to load