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javascrip对象中的函数callback对象中的�Ҏ(gu��)��

Sat, 21 Apr 2012 15:35:00 GMT

当在函数�c�M��的某一个对象，需要回调类中的某一个方法时�Q�可以通过如下方式实现�?br />Test = function(testFuncObj){

var testFunc = testFuncObj;

var _this = this;

this.render = function(parent){

testFunc.onClick(_this.onClick)

}

this.onClick = function(node){

alert(node.text);

}

沙漠中的�?/a> 2012-04-21 23:35 发表评论

javascript命��o(h��)行完成自动添加受信�Q站点

Fri, 18 Nov 2011 07:30:00 GMT

沙漠中的�?/a> 2011-11-18 15:30 发表评论

Thu, 21 May 2009 08:02:00 GMT

保证�|�站用户�Q�或��理员）(j��)在同一旉��只登陆一�ơ在很多场合是很必要的！下面举一个基于Java�q�_��实现的例子�?br /> �W�一步：(x��)创徏SessionListenter�c?/strong>

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import org.apache.log4j.Logger;
import org.jpxx.sw.Constants;
import org.jpxx.sw.Factory;

/** *//**
* 该监听器用于监听后台��理员登陆。只允许�l�一��理员在同一旉��登陆一�ơ�?br /> * @author Jun Li
* @version  $Revision: 1.0.2 $, $Date: 2009/01/05 $
* @since 1.0.0
*/
public class SessionListener implements HttpSessionListener {

    Logger log = Factory.getSingletonInstance().getLogger(SessionListener.class);
    public void sessionCreated(HttpSessionEvent event) {
    }

    public void sessionDestroyed(HttpSessionEvent event) {
        HttpSession session = event.getSession();
        // 获取存储��理员的session
        Object o = session.getAttribute(Constants.JPXX_ADMIN_LOGIN_USERNAME_SESSION);
        if(o!=null){
            String userName = o.toString();
            // 登陆的用户都存储在Hashtable中，用户退出，从Hashtable中删除该用户
            Factory.getUsers().remove(userName);
            log.error("删除用户�Q?/span>" + userName + "       " + new java.util.Date());
        }
    }
}

说明�Q�由于该�c�L��自于��目�Q�有很多操作都进行了(ji��n)��装�Q��?zh��n)��E�作修改卛_��正常使用。注释掉Logger�Q�声明一个静(r��n)态变量private static Hashtable user = new Hashtable();在sessionCreated()�Ҏ(gu��)��中将刚登陆的用户��d��到user中。�?zh��n)��q�需要写注销的页面（jsp或者servlet�Q�，在页面里面调用session.invalidate(); 该方法会(x��)触发sessionDestroyed()事�g�Q?br />
    �W�二部：(x��)��该监听器注册到web.xml

<listener>
        <listener-class>org.jpxx.sw.business.SessionListenerlistener-class>
listener>

说明�Q�仅仅依靠session监听器不可能100%可靠�Q�有可能用户不正帔R��?例如直接关闭��览器、系�l�断�늭��{?。针对直接关闭浏览器有如下解��x(ch��ng)��案：(x��)在被关闭的页面里面插入如下语句：(x��)

<body scroll="no" onUnload="Jpxx.forceLogout();" onbeforeunload="Jpxx.forceLogout();">

Jpxx.forceLogout()�Ҏ(gu��)��通过AJAX技术来强制注销用户�Q�即调用session.invalidate()�Ҏ(gu��)��?
转蝲:http://www.jpxx.org/?tid=54

沙漠中的�?/a> 2009-05-21 16:02 发表评论

Fri, 07 Nov 2008 08:25:00 GMT

判断是否全�ؓ(f��)汉字

if(/[^/x00-/xff]/g.test(s))
   alert("含有汉字");
else
   alert("全是字符");

var strTest="��试Test";
alert(strTest.length);
//昄��?�Q�他把一个汉字当作一自字�W�，而我需要得到的�l�果�?�Q�也��是把汉字当成两个字�W?/p>
var strTest="��试Test";
  alert(strTest.replace(/[^\x00-\xff]/g,'##').length);

以上�Ҏ(gu��)��只能求汉字加子母的情情况�Q��ؓ(f��)求��gؓ(f��)1的情况就�?x��)��生异�怺�(ji��n)

ADM.checkStrLen=function(value){
    var str,Num = 0;
    if(value==null)
        return Num;

    for (var i=0;i<value.length;i++){
        str = value.substring(i,i+1);
        if (str<="~")  //判断是否双字�?/span>
            Num+=1;
        else
            Num+=2;
    }

return Num;
}

以上�Ҏ(gu��)��能解��x(ch��ng)��字，字母�Q�数据�؜合的情况

沙漠中的�?/a> 2008-11-07 16:25 发表评论

�E�序讄��Extjs�?w��i)中CheckBox的选中和取消选中讄��

Wed, 20 Aug 2008 06:36:00 GMT

在Extjs中treepanel中树(w��i)节点为checkbox�cȝ��节时�Q�有时候我们需要用�E�序来设�|�他的选中和取消选中状�?br /> var nodes=tree.getChecked();
if(nodes && nodes.length){
for(var i=0;i   //讄��UI状态�ؓ(f��)未选中状�?br />   nodes[i].getUI().toggleCheck(false);
  //讄��节点属性�ؓ(f��)未选中状�?br />   nodes[i].attributes.checked=false;
}
}
�q�样通过获取已选择的节点，用程序取消选择状�?br /> 反之可以讄��未选中节点选中状�?/p>

沙漠中的�?/a> 2008-08-20 14:36 发表评论

Thu, 17 Jul 2008 09:23:00 GMT

While increasingly more websites are fully or partially based on AJAX, it is still difficult to develop complicated AJAX applications. What is the main issue which causes this difficulty in developing AJAX applications? Is it asynchronous communication with the server, or is it GUI programming? Both are routinely performed by desktop window applications -- so why is development of AJAX applications which do the same things particularly difficult?

Let’s consider this issue using a simple example. Suppose that you want to build a tree-structured bulletin board system which loads the data for each article by communicating with the server according to user requests rather than loading all articles at one time from the server. Each article has 4 pieces of information associated with it: a unique ID within the bulletin board system, the name of the person who posted the article, the content of the article, and an array of the IDs of its child articles. To begin with, let’s assume that there is a JavaScript function named getArticle() which is responsible for loading a single article. This function receives the integer ID of the article to be loaded as an argument, and it retrieves the data of the article with that ID from the server. It then returns an object which has the 4 pieces of information contained in that article: id, name, content, and children. An example of this function in use can be written like this:

function ( id ) {
var a = getArticle(id);
document.writeln(a.name + "
" + a.content);
}

As you may notice, calling this function many times with the same article ID, however, requires communications with the server again and again for no good reason. To counter this problem, consider the function getArticleWithCache(), which is a getArticle() with a cache capability. In this example, the data loaded by getArticle() will be simply retained as a global variable:

var cache = {};
function getArticleWithCache ( id ) {
if ( !cache[id] ) {
cache[id] = getArticle(id);
}
return cache[id];
}

Now the articles that have been read are cached. Now, let’s consider the function backgroundLoad(), which loads the data of all articles based on this mechanism. This function aims to preload all of the child articles in the background while the user is reading a given article. Because the article data is tree structured, a recursive algorithm can easily be written which traverses the tree and allows all articles to be loaded:

function backgroundLoad ( ids ) {
for ( var i=0; i < ids.length; i++ ) {
var a = getArticleWithCache(ids[i]);
backgroundLoad(a.children);
}
}

The backgroundLoad() function receives an array of IDs as an argument and applies our previously-defined getArticleWithCache() to each ID. This allows the data of the article corresponding to each ID to be cached. Then, by recursively calling backgroundLoad() on the IDs of the child articles of the loaded article, the entire article tree is cached.

So far, everything looks good. If you have worked on AJAX application development, however, you should know that this naïve implementation won’t work successfully. The example has been based on the tacit understanding that getArticle() uses synchronous communication. As a general rule, however, JavaScript requires the use of asynchronous communication in communicating with the server because it has only a single thread. In terms of simplicity, processing everything (including GUI events and rendering), on one thread is a good programming model, because it eliminates the need to think about the complicated problems associated with thread synchronization. On the other hand, it presents a significant problem in developing applications –which appear responsive to the user because the single-thread environment cannot respond to users’ mouse clicking and/or key operation when the thread is working on something else (such as the getArticle() call).

What happens if synchronous communication is carried out within this single-threaded environment? Synchronous communication stops the browser’s execution until the communication result is obtained. The thread cannot respond to users while waiting for the communication result because the call from the server has not been completed, and the thread will remain blocked until the call returns. For this reason, it can not respond to users while it is waiting for the server’s response and the browser therefore looks frozen. This also holds true for the execution of getArticleWithCache() and backgroundLoad(), which are based on getArticle(). Because may take a considerable amount of time to download all of the articles, the browser freezing during that time is a serious problem for backgroundLoad() - since the browser is frozen, it is not possible in the first place to achieve the goal of preloading the data in the background while users are reading articles, since the article will be unreadable.

Since the use of synchronous communication creates a significant problem in usability as described above, JavaScript uses asynchronous communication as a general rule. Therefore, let’s rewrite the program above based on asynchronous communication. JavaScript requires asynchronous communications to be written in an event-driven programming style. In most instances, you specify a callback function which is called once the communication response has been received. For example, getArticleWithCache() defined above can be rewritten as:

var cache = {};
function getArticleWithCache ( id, callback ) {
if ( !cache[id] ) {
callback(cache[id]);
} else {
getArticle(id, function( a ){
cache[id] = a;
callback(a);
});
}
}

This program also internally calls the getArticle() function. It should be noted, however, that the version of getArticle() which is designed for asynchronous communication expects to receive a function as the second argument. When this version of getArticle() is called, it sends a request to the server, as before, however the function returns immediately without waiting for a response from the server. This means that when the execution is returned to the caller, the server response has not yet been retrieved. This allows the thread to work on other tasks until the server response is obtained and the callback function is called. As soon as this response is received from the server, the callback function specified as the second argument of getArticle() is invoked with the server’s response as an argument. Likewise, getArticleWithCache() has been changed so that it will expect a callback function as the second argument. This callback function will then be called within the callback function that is passed to getArticle() so that it will be executed after the server-communication is finished.

You may think that the above rewriting alone is rather complicated, but the backgroundLoad() function involves even more complicated rewriting. It can be also rewritten to handle a callback function:

function backgroundLoad ( ids, callback ) {
var i = 0;
function l ( ) {
if ( i < ids.length ) {
getArticleWithCache(ids[i++], function( a ){
backgroundLoad(a.children, l);
});
} else {
callback();
}
}
l();
}

This rewritten backgroundLoad() function does not look much like our original function, however there is no difference in what they do. This means that both functions receive an array of IDs, call getArticleWithCache() on each element of the array, and recursively apply backgroundLoad() to the resultant child articles. However, it is not easy to recognize even the loop structure for the array, which was represented by a for-statement in the original program. Why are these two sets of functions that do the same thing so totally different from each other?

The difference results from the fact that any function must return immediately after any function that requires server-communication, such as getArticleWithCache(). The callback function that should receive the server response cannot be called unless the original function is no longer executing. For JavaScript, it is not possible to suspend the program in the middle of loops, such as for-statements, and resume it later at the point where execution was suspended; the loop is therefore represented by recursively passing the callback function instead of using a loop syntax. For those who are familiar with Continuation-Passing Style (CPS), this is a manual implementation of CPS. Because no loop syntax can be used, even the simple program described earlier that traverses a tree requires complicated statements. The problem associated with event-driven programs is known as the control flow problem: loop and other control flow statements are likely to be difficult to understand.

There is another problem: if you convert a function which does not use asynchronous communication into a function that uses asynchronous communication, the rewritten function will need to have a new parameter which is a callback functions. This poses a significant problem to existing APIs since our internal changes will not remain internal, but will result in broken APIs and changes by others using our API.

What is the root cause of all of these problems? That’s right. The fact that JavaScript has only one thread causes the problems. Carrying out asynchronous communication on only one thread requires an event-driven program and complicated statements. If another thread could respond to users while the program is waiting for the server response, acrobatics like this would not be required.

Invitation to Multithreaded Programming

Let me talk about Concurrent.Thread, a library that allows JavaScript to use multiple threads, since this greatly eases the difficulty associated with asynchronous communication in the AJAX development mentioned above. This is a free-software library implemented in JavaScript, available under the Mozilla Public License / GNU General Public License. You can download the source code from the website.

Let’s download and use the source code right away. Suppose that you have saved the downloaded source code as a file named Concurrent.Thread.js. Before doing anything else, let’s run the program below, which has a very naïve implementation:

Executing this program should display numbers starting with 0 in order. Numbers appear one after another, which you can view by scrolling the page. Now, let’s look at the source code in more detail. It uses a simple infinite loop as indicated by while ( 1 ). In ordinary cases, a JavaScript program like this continues to use the one and only thread, causing the browser to look frozen. Naturally, it does not allow you to scroll the screen. Then, why does the above program allow you to scroll? The key is Concurrent.Thread.create() located above while ( 1 ). This is a method provided by the library; it is for creating a new thread. On a new thread, the function passed as the argument is executed. Let me slightly rewrite the program as follows:

In this program we have a new function f(), which shows numbers repeatedly. This is defined at the top, and the create() method is called twice with f() as arguments. The second argument passed to the create() method is passed to f() without modification. Executing this program shows some small numbers starting with 0, which are followed by some large numbers starting with 100,000 and small numbers again that follow up the first series of small numbers. Like this, you can observe that the program shows alternating lines of small numbers and large numbers. This indicates that two threads are running concurrently.

Let me show you another use of Concurrent.Thread. In the above example, the create() method was called to create a thread. It is also possible to create a thread without calling any library APIs at all. For example, the former example can be expressed as:

Inside the script tag, an infinite loop is written simply in JavaScript. You should take note of the type attribute of the tag: an unfamiliar value (text/x-script.multithreaded-js) is assigned to it. If this attribute is assigned to the script tag, then Concurrent.Thread executes the content of the tag on a new thread. You should remember that, in this case as well, the library body of Concurrent.Thread must be included.

With Concurrent.Thread, it is possible to switch execution context from one thread to another as needed even if you write a long and continuous program. Let me briefly talk about how this behavior is achieved. In short, code conversion is used. Very roughly speaking, the function passed to the create() method is first converted to a character string, which is then rewritten so that it can be executed on a piecemeal basis. Then, the rewritten function is executed little by little on the scheduler. The scheduler is responsible for coordinating multiple threads. In other words, it makes adjustments so that each of the rewritten functions will be evenly executed. Concurrent.Thread actually does not create new threads but simply simulates a multi-threaded environment on the original single thread.

Although the converted functions appear to be running on different threads, there is actually only one thread running everything. Carrying out synchronous communication within the converted functions will still cause the browser to freeze. You may think that our original problem has not been solved at all, however you don’t have to worry. Concurrent.Thread provides a purpose-built communications library which is implemented using the asynchronous JavaScript communication style and which is designed to allow the other threads to work even when a thread is waiting for a response from the server. This communications library is found under the Concurrent.Thread.Http namespace. For example, it is used as follows:

The get() method retrieves the content of the specified URL using HTTP GET, as its name suggests. It takes a target URL as the first argument and an array representing HTTP header fields as the optional second argument. The get() method communicates with the server and returns an XMLHttpRequest object as the return value when it has received the server response. When the get() method returns, the response had been received. It is not necessary to use a callback function to receive the result. Naturally, there is no worry that the browser freezes while the program is waiting a response from the server. In addition, the post() method can be used to send data to the server:

The post() method takes a destination URL as the first argument and content body to be sent as the second argument. As with the get() method, you can also assign header fields by the optional third argument.

If you implement getArticle() in the first example using this communications library, then you can quickly write getArticleWithCache(), backgroundLoad(), and other functions that use getArticle() using the naïve method shown at the beginning of this article. Even when that version of backgroundLoad() is reading article data, another thread can respond to users as a matter of course, and the browser therefore does not freeze. Now, do you understand how useful it is to use multiple threads in JavaScript?

转蝲:http://www.infoq.com/articles/js_multithread

沙漠中的�?/a> 2008-07-17 17:23 发表评论

Tue, 10 Jun 2008 08:27:00 GMT

最�q�研�I�createElement的时候发��C��个奇怪的问题

var echkbox=document.createElement("input");
echkbox.setAttribute("type","checkbox");
echkbox.setAttribute("id","inputid");
echkbox.setAttribute("name","inputname");
echkbox.setAttribute("value","inputvalue");
echkbox.setAttribute("checked","checked");
var addhere=document.getElementById("someElementId");
addhere.appendChild(echkbox);
alert(document.getElementById("inputid").checked);

ie7昄��出来的checkbox居然是未选中的但是alert出来的却是true�Q�而FF一切正�?br /> 后来查了(ji��n)半天资料说是ie昄��的时候只对状态改变比较敏�?br /> �Ҏ(gu��)��
var echkbox=document.createElement("input");
echkbox.setAttribute("type","checkbox");
echkbox.setAttribute("id","inputid");
echkbox.setAttribute("name","inputname");
echkbox.setAttribute("value","inputvalue");
var addhere=document.getElementById("someElementId");
addhere.appendChild(echkbox);
echkbox.setAttribute("checked","checked");
alert(document.getElementById("inputid").checked);

一切ok
radio同样是这�U�情��c(di��n)�?/font>
转自 someone's something�I�间

沙漠中的�?/a> 2008-06-10 16:27 发表评论

float在IE和firefox中的使用

Mon, 26 May 2008 11:09:00 GMT

在IE和firefox中，�Ҏ(gu��)��档对象DIV标签的停靠方式不�?如在IE中他��p��别float的属性，但是在firefox中他��需�?/font>cssFloat

firefox下代�?/p>
var
oDiv=document.createElement("div");
oDiv.style.width="101";
var iDiv1=document.createElement("div");           iDiv1.style.background="#FFEE00";
iDiv1.style.width=50;    iDiv1.style.cssFloat="left";    iDiv1.innerHTML="双��";
iDiv1.style.height="20"; oDiv.appendChild(iDiv1);

var iDiv2=document.createElement("div");
iDiv2.style.background="#881200";
iDiv2.style.width=50;
iDiv2.style.cssFloat="left";
iDiv2.innerHTML="中间�?/span>";
iDiv2.style.height="20";
oDiv.appendChild(iDiv2);

var iDiv3=document.createElement("div");
iDiv3.style.background="#235500";
iDiv3.style.width=1;
iDiv3.style.height="20";
iDiv3.style.cssFloat="left";
iDiv3.style.overflow="hidden";
oDiv.appendChild(iDiv3);

document.getElementById("test").innerHTML=oDiv.innerHTML;

IE代码

var
oDiv=document.createElement("div");         oDiv.style.width="101";
var
iDiv1=document.createElement("div");           iDiv1.style.background="#FFEE00";
iDiv1.style.width=50;    iDiv1.style.float="left";    iDiv1.innerHTML="双��";
iDiv1.style.height="20"; oDiv.appendChild(iDiv1);

var iDiv2=document.createElement("div");
iDiv2.style.background="#881200";
iDiv2.style.width=50;
iDiv2.style.float="left";
iDiv2.innerHTML="中间�?/span>";
iDiv2.style.height="20";
oDiv.appendChild(iDiv2);

var iDiv3=document.createElement("div");
iDiv3.style.background="#235500";
iDiv3.style.width=1;
iDiv3.style.height="20";
iDiv3.style.float="left";
iDiv3.style.overflow="hidden";
oDiv.appendChild(iDiv3);

document.getElementById("test").innerHTML=oDiv.innerHTML;

沙漠中的�?/a> 2008-05-26 19:09 发表评论

Mon, 26 May 2008 10:56:00 GMT
在不同的�q�_��和不同的��览器中对javascript的支持也不同�Q�在我们写javascript�q�程中，需要尽量避免他的不兼容性，一般都采用最��公母法�Q�尽量满��不同��^台和不同��览器的我需要，但是对于某些特定功能�Q�我��需要在不同的浏览中实现不同的方法，因此我们��必��能实别不同的��^台和��览�?br /> 如下��是适别不同的��^台和��览器方�?br /> //��览器版�?br /> ADM.BROWERVERSION=parseInt(navigator.appVersion);
//是否为NETSCAPE��览�?br /> ADM.ISNETSCAPE=navigator.appName.indexOf("Netscape")!=-1;
//是否为IE��览�?br /> ADM.ISIE=navigator.appName.indexOf("Microsoft")!=-1;
//代理
ADM.AFENT=navigator.appName.toLowerCase();
//是否为WINDOWS�q�_��?br /> ADM.ISWINDOWS=ADM.AFENT.indexOf("win")!=-1;
//是否为MAC�q�_��?br /> ADM.ISMAC=ADM.AFENT.indexOf("mac")!=-1;
//是否为UNIX�q�_��?br /> ADM.ISUNIX=ADM.AFENT.indexOf("x11")!=-1;

沙漠中的�?/a> 2008-05-26 18:56 发表评论

�?w��i)�{化�ؓ(f��)表格囑֞�展现

Sat, 10 May 2008 14:04:00 GMT
        做过olap开发的人可能都知道�Q�他查出来的表的�l�构��是一��|��(w��i)�Q�我们需要把�?w��i)�{化�ؓ(f��)表，通过表格的样式用囑֞�更加客观的展现出�?/span>
我们有一��这��L(f��ng)��?/span>

我们现在要把�q�棵�?w��i)�{化成如下的表格样�?/span>

通过表格我们可以看出�Q�他有三部䆾�Q�主栏，宾栏�Q�主体，而主栏，是一颗向叛_��开的树(w��i)�Q�宾栏是一颗向下展开的树(w��i)�Q�而主体部份则是一个表�?/span>

表格的整体布局

��L��

HTML�l�构




李宁DIV>










�?/span>/DIV>




上衣DIV>







宾栏

HTML�l�构




大区










华北




华中







��M��

HTML�l�构




l









其中在HTML中边框全部采用宽度或高度�?PX的DIV构成
在div布局中，横向展开采用的属性是float="left"

我设计的Js�cȝ��构图如下

一个由�?w��i)�{化�ؓ(f��)表格的程序就完成�Q�但是在开发过�E�中�Q�有时候也��到一些问题，如效率等�Q�如有哪位对�q�控件或报表开发方面有兴趣的，大家一起交��?span lang="EN-US">

沙漠中的�?/a> 2008-05-10 22:04 发表评论

Mon, 05 May 2008 15:05:00 GMT

什么是Firebug

从事�?ji��n)数�q�的Web开发工作，��来��觉得现在对WEB开发有�?ji��n)更高的要求。要写出漂亮的HTML代码�Q�要�~�写�_�致的CSS样式表展�C�每个页面模块；要调�?a >javascript�l�页面增加一些更�z�L��的要素；要��用Ajax�l�用户带来更好的体验。一个优�U�的WEB开发�h员需要顾�?qi��ng)更多层面，才能交出一份同样优�U�的作业。�ؓ(f��)帮助�q�大正处于Web2.0�z�流中的开发�h员，在这里�ؓ(f��)大家介绍一�ƾ轻巧灵�zȝ��辅助开发工兗��?/p>
Firebug是Firefox下的一�Ƒּ�发类插�g�Q�现属于Firefox的五星��强力推荐插�g之一。它集HTML查看和编辑、Javascript控制台、网�l�状�늛�视器于一体，是开发JavaScript、CSS、HTML和Ajax的得力助手。Firebug如同一把精巧的瑞士军刀�Q�从各个不同的角度剖析Web��面内部的细节层面，�l�Web开发者带来很大的便利。这是一�ƾ让人爱不释手的插�g�Q�如果你以前没有接触�q�它�Q�也许在阅读本文之后�Q�会(x��)有一试的�Ʋ望。笔者在撰写此文的时候，正逢Firebug发布1.0正式版，�q�不能不说是�U��y合�?br />

应用

Firebug插�g虽然功能强大�Q�但是它已经和Firefox��览器无�~�地�l�合在一��P��使用��单直观。如果你担心(j��)它会(x��)占用太多的系�l�资源，也可以方便地启用/关闭�q�个插�g�Q�甚至针对特定的站点开启这个插件�?/p>
在安装好插�g之后�Q�先用Firefox��览器打开需要测试的��面�Q�然后点��d��下方的绿色按钮或使用快捷键F12唤出Firebug插�g�Q�它�?x��)将当前��面分成上下两个框架�Q�如�?所�C��?/p>
�?�Q�Firebug插�g展开囄��

从图1中看刎ͼ�Firebug�?个主要的Tab按钮�Q�下文将主要介绍介绍�q�几斚w��的功能�?/p>

Console HTML CSS Script Dom Net

控制�?/td> Html查看�?/td> Css查看�?/td> 脚本条时�? Dom查看�?/td> �|�络状况监视

Console 控制�?/h3>
控制台能够显�C�当前页面中的javascript错误以及(qi��ng)警告�Q��ƈ提示出错的文件和行号�Q�方便调试，�q�些错误提示比�v��览器本�w�提供的错误提示更加详细且具有参考�h(hu��n)倹{��而且在调试Ajax应用的时候也是特别有用，你能够在控制台里看到每一个XMLHttpRequests��h��post出去的参数、URL�Q�http头以�?qi��ng)回馈的内容�Q�原本似乎在�q�后黑匣子里�q�作的程序被清清楚楚地展�C�在你面前�?/p>
象C shell或Python shell一��P��你还能在控制��C��查看变量内容�Q�直接运行javascript语句�Q�就��是大段的javascript�E�序也能够正��运行�ƈ拿到�q�行期的信息�?/p>
控制台还有个重要的作用就是查看脚本的log, 从前你也�怹�(f��n)惯了(ji��n)使用alert来打印变量，但是Firebug�l�我们带来了(ji��n)一个新朋友 —�?console.log, 最��单的打印日志的语法是�q�样的：(x��)

PLAIN TEXT

CODE:

console.log("hello world")

如果你有一堆参数需要组合在一赯��出，可以写成�q�样�Q?/p>
PLAIN TEXT

CODE:

console.log(2,4,6,8,"foo",bar).

Firebug的日志输出有多种可选的格式以及(qi��ng)语法�Q�甚臛_��以定制彩色输出，比�v单调的alert�Q�显然更加方便，限于��幅�Q�这里不做详�l�说明，但是有志于提高debug效率的读者，可以到Firebug的官方站点（见附录）(j��)查看更详�l�的教程�?/p>
�?�Q?在控制台里调试javascript

查看和修改HTML

�W�一�ơ看到Firebug强大的HTML代码查看器，��p��得它与众不同�Q�相比于Firefox自带的HTML查看器，它的功能强大�?ji��n)许多�?HTML

首先你看到的是已�l�经�q�格式化的HTML代码�Q�它有清晰的层次�Q�你能够方便地分辨出每一个标�{�之间的从属�q�行关系�Q�标�{��折叠功能能够帮助你集中精力分析代码。源代码上方�q�标记出�?ji��n)DOM的层�ơ，如图3所�C�，它清楚地列出�?ji��n)一个hml元素的parent、child以及(qi��ng)root元素�Q�配合F(tu��n)irebug自带的CSS查看器��用，�?x��)给div+css��面分析�~�写带来很大的好处。你�q�可以在HTML查看器中直接修改HTML源代码，�q�在��览器中�W�一旉��看到修改后的效果�Q�光凭这一点就�?x��)让许多��面设计师死心(j��)塌地地成��?f��)Firebug的粉丝了(ji��n)�?/p>
有时候页面中的javascript�?x��)根据用��L(f��ng)��动作如鼠标的onmouseover来动态改变�(sh��)��些HTML元素的样式表或背景色�Q�HTML查看器会(x��)��页面上改变的内容也抓下来，�q�以黄色高�(sh��)��标记�Q�让�|�页的暗��操作彻底成为历双Ӏ?/p>
利用Inspect��(g��)查功能，我们�q�可以用鼠标在页面中直接选择一些区块，查看相应的HTML源代码和CSS样式表，真正的做到所见即所得，如果你��用了(ji��n)外部�~�辑器修改了(ji��n)当前�|�页�Q�可以点击Firebug的reload囄��重新载入�|�页�Q�它�?x��)��l�跟�t�你之前用Inspect选中的区块，方便调试�?/p>
�?:�Q�HTML查看�?br />

CSS调试

Firebug的CSS调试器是专�ؓ(f��)�|�页设计师们量��n定做的�?/p>
如今的网��设计言必称div+css�Q�如果你是用table套出来的HTML��面�Q�就得按�q�规矩重构一遍，否则昑־�你不够时髦！用div做出来的��面的确能精��HTML代码�Q�HTML标签减肥的结果就是CSS样式表的�~�写成了(ji��n)��面制作的重头戏。Firebug的CSS查看器不仅自下向上列出每一个CSS样式表的从属�l�承关系�Q�还列出�?ji��n)每一个样式在哪个样式文�g中定义。你可以在这个查看器中直接添加、修攏V��删除一些CSS样式表属性，�q�在当前��面中直接看��C��改后的结果�?/p>
一个典型的应用��是��面中的一个区块位�|�显得有些不太恰当，它需要挪动几个象素。这时候用CSS调试工具可以��L��~�辑它的位置——你可以�Ҏ(gu��)��需要随意挪动象素�?br /> 如图4中正在修改一个区块的背景艌Ӏ?/p>
提示�Q�如果你正在学习(f��n)CSS样式表的应用�Q�但是总记不住常用的样式表有哪些��|��可以��试在CSS调试器中选中一个样式表属性，然后用上下方向键来改变它的��|��它会(x��)把可能的��g��个个遍历�l�你看�?/p>
�?: CSS查看器，能够直接修改样式�?br />

可视化的CSS��标

我们可以利用Firebug来查看页面中某一区块的CSS样式表，如果�q�一步展开右侧Layout tab的话�Q�它�?x��)以标尺的�Ş式将当前区块占用的面�U�清楚地标识出来�Q�精��到象素�Q�更让�h惊讶的是�Q�你能够在这个可视化的界面中直接修改各象素的��|��面上区块的位置��׃��(x��)随改动而变化。在��面中某些元素出现错位或者面�U�超出预料值时�Q�该功能能够提供有效的帮助，你可以籍此分析offset、margin、padding、size之间的关�p�，从而找�?gu��)��决问题的办法�?/p>
�?�Q�Firebug中的CSS标尺

�|�络状况监视�?/h3>
也许有一天，你的老板或者客��h��C��Q�抱怨你制作的网��速度奇慢�Q�你该如何应对？你或�怼�(x��)说这可能是网�l�问题，或者是�?sh��)脑配置问题�Q�或者是�E�序太慢�Q�或者直说是他们的�h品问题？不管怎么��_(d��)��最后你可能被要求去解决�q�个有多�U�可能的问题�?/p>
�|�络状况监视器能帮你解决�q�个��手问题。Firebug的网�l�监视器同样是功能强大的�Q�它能将��面中的CSS、javascript以及(qi��ng)�|�页中引用的囄��载入所消耗的旉��以矩状图呈现出来�Q�也许在�q�里你能一把揪出拖慢了(ji��n)你的�|�页的元�Ӟ��q�而对�|�页�q�行调优�Q�最后老板满意客户�Ƣ喜�Q�你的饭��也因此而牢固�?/p>
�|�络监视器还有一些其它细节功能，比如预览囄��Q�查看每一个外部文件甚��x(ch��ng)��xmlHttpRequests��h��的http头等�{��?/p>
�?�Q�网�l�状�늛�视器

Javascript调试�?/h3>
�q�是一个很不错的javascript脚本调试器，占用�I�间不大�Q�但是单步调试、设�|�断炏V��变量查看窗口一个不��。正所谓麻雀虽小�Q�五脏俱全�?/p>
如果你有一个网站已�l�徏成，然而它的javascript有性能上的问题或者不是太完美�Q�可以通过面板上的Profile来统计每�D�脚本运行的旉��Q�查看到底是哪些语句执行旉��q�长�Q�一步步排除问题�?/p>
�?�Q�javascript调试�?br />

DOM查看�?/h3>
DOM(Document Object Model)里头包含�?ji��n)大量的Object以及(qi��ng)函数、事�Ӟ��在从前，你要想从中查到需要的内容�Q�绝非易事，�q�好比你��M��(ji��n)一个巨大的图书馆，惌��扑ֈ�几本名字不太��切的小书，众多的选择�?x��)让你无所适从。而��用Firebug的DOM查看器却能方便地��览DOM的内部结构，帮助你快速定位DOM对象。双��M��个DOM对象�Q�就能够�~�辑它的变量或��|��~�辑的同�Ӟ��你可能会(x��)发现它还有自动完成功能，当你输入document.get之后�Q�按下tab键就能补齐�ؓ(f��)document.getElementById�Q�非常方�ѝ��如果你认�ؓ(f��)补齐得不够理惻I��按下shift+tab又会(x��)恢复原状。用�?ji��n)Firebug的DOM查看器，你的javascript从此扑ֈ��?ji��n)驱使的对象�Q�W(xu��)eb开发也许就成了(ji��n)一件乐事�?/p>
�?: Dom查看�?br />

��结

Firebug插�g提供�?ji��n)一整套web开发所必需的工兗��从HTML的编写，到CSS样式表的��化调优�Q�以�?qi��ng)用javascript脚本开发，亦或是Ajax应用�Q�Firebug插�g都会(x��)成�ؓ(f��)你的得力助手。所谓工�Ʋ善其事�Q�必先利其器。在Web2.0的时代，�a�必称Ajax�Q�动辄就是用户体验提升，如果把Firebug工具用好�Q�必能让你如虎添��|��HTML、CSS、javascript整理得服服帖帖，从此成�ؓ(f��)web开发中的专家��人物�?/p>
�?/h3>
Firebug的中文含义是萤火虫，作者是Joe Hewitt�Q�官方网��?http://www.getfirebug.com
Firefox亦即火狐��览器，是近�q�来撼动IE��览器市(j��ng)场占有率的一支强大力量，要不是它的出玎ͼ�我想有生之年说不定也看不到IE 7的发布了(ji��n)�Q�官方网��?http://www.firefox.com
引用:http://www.ooso.net/index.php/archives/294

沙漠中的�?/a> 2008-05-05 23:05 发表评论

javascript�~�辑器和调试工具

Mon, 05 May 2008 15:03:00 GMT

         最�q�在做javascript开发，��x(ch��ng)��一个比较好的javasctipt�~�辑器，在网上看��C��(ji��n)�?st JavaScript Editor 的评价不错，集成代码自动弹出昄��Q�验证错误功能。可以说是最好的一个javascript�~�辑器了(ji��n)�Q�于是把它下下来�Q�用��h��实�q��(sh��)��错，对于javascrtipt初学者还是javasctipt工程师，��用这个工兗��?br />

          但是他对��(g��)错方面没有myesclipse的好�Q�对于有一些警告和错误它不能提�C�出�?/p>
          对于javasctipt调试工具�Q�也有好几种可选择的方�?�׃��机器比较慢，我采用的是firefox+firebug来调试，在网上找�?ji��n)一��介�l�的文�g�Q�等下把它帖出来�Q�开�?Net的�h都知道，vs是一个很不错的调试javasctipt工具�Q�我以前也一直用�q�个来调试javasctipt,不过专门用来调试javasctipt�Q�可以说是大材小用了(ji��n)

沙漠中的�?/a> 2008-05-05 23:03 发表评论

Dom-Drag学习(f��n)

Thu, 24 Apr 2008 06:41:00 GMT
     摘要: 如果你想实现Web上的�l��g能用鼠标随意拖动到页面的��L��位置或指定的位置�{�，那你��p��看看dom-drag.js�?ji��n)。dom-drag.js可以从http://youngpup.net/projects/dom-drag/下蝲刎ͼ�作�?Aaron Boodman�?         其作者称其�ؓ(f��)面向��C��DHTML��览器的�?..  阅读全文

沙漠中的�?/a> 2008-04-24 14:41 发表评论

JavaScript之实现私有属性、像C++和Java一��h��持基于类的��承方法之例子

Thu, 24 Apr 2008 06:29:00 GMT
     摘要: 前面已经�?ji��n)解刎ͼ�JavaScript中也可以实现�U�有属性，而且JavaScript也能像C++和Java一��h��持基于类的��承方法。�ؓ(f��)�?ji��n)展�C��些是怎样实现的，下面说明如何转换前面使用Vehicle、SportsCar和CementTruck对象的示例，从而��用信息隐藏和�l�承的新模式。代码清�?-5列出�?ji��n)新的对象定义�?代码清单5-5　classicalInheritance.js funct...  阅读全文

沙漠中的�?/a> 2008-04-24 14:29 发表评论

Thu, 24 Apr 2008 06:21:00 GMT

JavaScript中基于prototype的��承机制可以很好地工作�Q�但是对于一些已�l�习(f��n)惯于C++和Java�{�语�a�中基于类的��承机制的人来��_(d��)��JavaScript的prototype�l�承机制不是一�U�自然的�~�程�Ҏ(gu��)��。如果你不想用基于prototype的��承，而想用一�U�基于类的��承方法，那就�l�箋(hu��)��M��d��?br /> Netscape的Bob Clary[4]也提��Z��(ji��n)一个方法，它可以��一个对象��用一个通用的脚本从另一个对象��承属性和函数。这个脚本只是将“�?#8221;对象的属性和函数��单地复制�?#8220;�?#8221;对象。�ؓ(f��)此，我们��说明如何对脚本�E�加修改�Q�从而只是将子对象中不存在的属性和函数复制到子对象�Q�这样一来，子对象中的函数就能覆盖父对象的函数。在两个对象之间创徏�l�承关系的通用函数如下�Q?br /> function createInheritance(parent, child) {
    var property;
    for(property in parent) {
        if(!child[property]) {
            child[property] = parent[property];
        }
    }
}
createInheritance函数有两个参敎ͼ�父对象和子对象。这个函数只是�P代处理父对象的所有成员（成员��是属性或函数�Q�，如果某个成员在子对象中不存在�Q�则复制到子对象�?br /> 使用createInheritance函数相当��单：(x��)首先创徏子对象的一个实例，然后使用createInheritance函数�Q��ؓ(f��)它传递子对象以及(qi��ng)父对象的一个实例，如下�Q?br /> var child = new Child();
createInheritance(new Parent(), child);
父对象中有而子对象中没有的所有属性和�Ҏ(gu��)��复制到子对象�?/font>

引用:http://book.csdn.net/bookfiles/11/100117056.shtml

沙漠中的�?/a> 2008-04-24 14:21 发表评论

JavaScript�U�有属性和使用JavaScript的信息隐�?

Thu, 24 Apr 2008 06:04:00 GMT

        铁杆的面向对象设计支持者会(x��)注意刎ͼ�当��用prototype�Ҏ(gu��)��向JavaScript对象增加属性和函数�Ӟ��所增加的属性和函数都是公用的，所有其他对象都能访问。对于函数来��_(d��)��q�通常没有问题�Q�因为大多数函数都确实应当提供给外部客户。但是对于属性，面向对象设计的支持者就�?x��)指出，公有属性违反了(ji��n)信息隐藏的概念，对象的属性应当是�U�有的，因此外部客户不能直接讉K��。外部客户只能通过公用可用的函数来讉K��对象的私有属性�?/font>

对于JavaScript�Q�同��h��可能创徏外部客户不能讉K��的私有属性，而只能通过对象的（公用�Q�方法来讉K��Q�但�q�一点很��有人知道。Douglas Crockford[3]提出�?ji��n)一�U�在JavaScript中创建私有属性的�Ҏ(gu��)��。这�U�方法非常简单，�ȝ��如下�Q?/font>

l    �U�有属性可以在构造函��C��使用var关键字定义�?/font>

l    �U�有属性只能由�Ҏ(gu��)��函数�Q�privileged function�Q�公用访问。特权函数就是在构造函��C��使用this关键字定义的函数。外部客户可以访问特权函敎ͼ�而且�Ҏ(gu��)��函数可以讉K��对象的私有属性�?/font>

下面来考虑前一个示例中的Vehicle�c�R��假设你惌��wheelCount和curbWeightIn- Pounds属性是�U�有的，�q�只能通过公用�Ҏ(gu��)��讉K��。新的Vehicle对象如代码清�?-4所�C��?/font>

代码清单5-4 重写后的Vehicle对象

function Vehicle() {

    var wheelCount = 4;

    var curbWeightInPounds = 4000;

    this.getWheelCount = function() {
        return wheelCount;
    }

    this.setWheelCount = function(count) {
        wheelCount = count;
    }

    this.getCurbWeightInPounds = function() {
        return curbWeightInPounds;
    }

    this.setCurbWeightInPounds = function(weight) {
        curbWeightInPounds = weight;
    }

    this.refuel = function() {
        return "Refueling Vehicle with regular 87 octane gasoline";
    }

    this.mainTasks = function() {
        return "Driving to work, school, and the grocery store";
    }
}

注意�Q�wheelCount和curbWeightInPounds属性都在构造函��C��使用var关键字定义，�q�就使得�q�两个属性是�U�有属性。属性不再是公用的，如果想通过点记法访问wheelCount属性的��|��如下�Q?/font>

var numberOfWheels = vehicle.wheelCount;

��׃��(x��)�q�回undefined�Q�而不是wheelCount实际的倹{�?/font>

�׃��属性现在是�U�有的，因此需要提供能讉K��q�些属性的公用函数。getWheelCount、setWheelCount、getCurbWeightInPounds和setCurbWeightInPounds函数��是作此使用的。现在Vehicle对象可以保证只能通过公用函数讉K��U�有属性，因此满��?ji��n)信息隐藏�?/font>

引用:http://book.csdn.net/bookfiles/11/100117056.shtml

沙漠中的�?/a> 2008-04-24 14:04 发表评论

Console	HTML	CSS	Script	Dom	Net
控制�?/td>	Html查看�?/td>	Css查看�?/td>	脚本条时�?	Dom查看�?/td>	�\|�络状况监视

仙踪林久久久久久久999,在线精品亚洲欧美日韩国产,一本大道香蕉久在线播放29

javascrip对象中的函数callback对象中的�Ҏ(gu��)��

javascript命��o(h��)行完成自动添加受信�Q站点

�E�序讄���Extjs�?w��i)中CheckBox的选中和取消选中讄���

Invitation to Multithreaded Programming

float在IE和firefox中的使用

�?w��i)�{化�ؓ(f��)表格囑֞�展现

什么是Firebug

应用

查看和修改HTML

CSS调试

可视化的CSS���标

���结

javascript�~�辑器和调试工具

Dom-Drag学习(f��n)

JavaScript之实现私有属性、像C++和Java一��h��持基于类的��承方法之例子

JavaScript�U�有属性和使用JavaScript的信息隐�?

�E�序讄��Extjs�?w��i)中CheckBox的选中和取消选中讄��

可视化的CSS��标

��结