将网络应用程序从Internet Explorer移植到Mozilla

校对中

简介

当Netscape最初推出Mozilla浏览器的时候, 特别考虑对W3C标准的支持. 所以Mozilla并不对Netscape Navigator 4.x 和微软IE遗留的源码做向后支持. 例如, Mozilla不支持<layer>, 我在后面会进行讨论. 那些像IE4一样, 在W3C标准概念之前开发的浏览器遗留了很多毛病. 在这篇文章里, 我将描述Mozilla的"Quirks Mode". 这个模式对IE和其他遗留下来的浏览器提供强大的向后HTML源码兼容性.

我还会概括一些非标准的技术. 比如XMLHttpRequest和富文本编辑那些Mozilla支持, 但到目前为止还没有W3C标准的(技术). 它们包括:

基本跨浏览器编程技巧

尽管网络标准明确存在, 不同浏览器表现还是不同 (其实, 同一浏览器在不同操作系统上也可能不一样). 很多浏览器, 包括IE, 也支持W3C之前的API, 并从没广泛地为W3C兼容的API进行支持.

在我详细论述Mozilla和IE的不同之前, 我要先讲一下一些关于如何令网络应用程序可以扩展来对今后新的浏览器支持的基本方法.

因为不同浏览器有时针对相同的功能, 使用不同的API, 你经常可以在源码中找到多个用来区分浏览器的if() else()的语句块. 下面这段源码是针对IE的 (只有用IE才被解析) :

. . . 

var elm; 

if (ns4) 
  elm = document.layers["myID"]; 
else if (ie4) 
  elm = document.all["myID"]

上面的源码是不可扩展的, 所以如果你想让它支持某个新的浏览器, 你必须把所有类似这样的源码块更新.

想消除每有新浏览器就要重新编写的问题, 最简单的方法就是抽取这个功能. 相比于多个if() else(), 你应该将常用任务抽取成独立的函数, 来提高效率. 这不仅让你的源码简单易读, 更简化了对新浏览器增加支持(的步骤):

var elm = getElmById("myID"); 

function getElmById(aID){ 
  var element = null; 

  if (isMozilla || isIE5) 
    element = document.getElementById(aID);
  else if (isNetscape4) 
    element = document.layers[aID];
  else if (isIE4) 
    element = document.all[aID];

  return element; 
} 

以上的代码仍然有“浏览器监听”的问题,即探测用户正在使用哪一个浏览器。浏览器监听通常通过用户代理完成,例如:

Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5) Gecko/20031016 

使用用户代理监听浏览器提供了使用中的浏览器的详细信息,然而当浏览器的新版本来临时,处理用户代理的代码经常出错,这样就需要修改代码。

如果浏览器的种类无关紧要(假设你已经阻止了不被支持的浏览器访问网络应用),使用浏览器的能力或对象的特色支持来进行监听更好也更可靠。你通常可以JavaScript中测试必需的功能来做到这一点。例如,比起以下的代码:

if (isMozilla || isIE5) 

你将更愿意使用:

if (document.getElementById) 

这将允许支持W3C标准规范的浏览器(例如Opera或Safari)无须改动地工作。

然而,用户代理监听只有在精确度显得重要时才有意义,例如在你审核一个浏览器是否符合网络应用程序的版本要求或试图解决bug的情况下。

JavaScript也允许顺序条件语言(inline conditional statements)以助于代码的可读性:

var foo = (condition) ? conditionIsTrue : conditionIsFalse; 

例如,你可以使用以下代码来取回一个单元(element):

 
function getElement(aID){ 
  return (document.getElementById) ? document.getElementById(aID)
                                   : document.all[aID];
} 

标题正文

Mozilla和Internet Explorer的区别

首先,我要讨论HTML在Mozilla和Internet Explorer中表现的区别。

工具提示(Tooltips)

传统浏览器将工具提示引进HTML中,在链接上显示它们,并使用alt属性的值作为工具提示的内容。最新的W3C HTML规范创造了title属性,意欲包含链接的详细描述。现代浏览器将使用title属性来显示工具提示,且Mozilla只支持为此属性显示工具提示而不支持alt属性。

实体(Entities)

HTML markup can contain several entities, which the W3C web standards body has defined. You can reference entities through their numerical or character reference. For example, you can reference the white space character #160 with &#160; or with its equivalent character reference &nbsp;.

HTML 置标包含了W3C 网页标准体定义的几个标准。你可以通过引用数字或字符来引用实体。例如,你可以使用&#160;以引用白色空格字符#160;或使用它的等价字符引用&nbsp;

Some older browsers, such as Internet Explorer, had such quirks as allowing you to use entities by replacing the ; (semi-colon) character at the end with regular text content:

某些旧式浏览器如Internet Explorer,有这样的惯例,即允许在常规文本内容末尾替换;(分号)字符以使用实体:

&nbsp Foo 
&nbsp&nbsp Foo 

Mozilla will render the above &nbsp as white spaces, even though that is against the W3C specification. The browser will not parse a &nbsp if it is directly followed by more characters, for example:

Mozilla提供上述&nbsp作为白色空格,即便这违反了W3C规范。如果&nbsp后直接连着更多的字符,浏览器不会解析此代码,例如:

&nbsp12345 

This code does not work in Mozilla, since it goes against the W3C web standards. Always use the correct form (&nbsp;) to avoid browser discrepancies.

这段代码在Mozilla中无效,因为它违反了W3C标准。请始终使用正确的格式(&nbsp;) 以避免浏览器不兼容。

文档对象模型(DOM)差异

The Document Object Model (DOM) is the tree structure that contains the document elements. You can manipulate it through JavaScript APIs, which the W3C has standardized. However, prior to W3C standardization, Netscape 4 and Internet Explorer 4 implemented the APIs similarly. Mozilla only implements legacy APIs if they are unachievable with W3C web standards.
文档对象模型(DOM)通常就是包含所有文档元素的树型结构体。开发者可以用一些javascript API来控制这个结构体,当然这些API是基于W3C标准的。在W3C标准公布前Netscape 4和IE 4 就实现了相似的功能,而Mozilla仅仅实现了一些没有成为最终标准的API。

文档对象模型(DOM)通常就是包含所有文档元素的树型结构体。开发者可以用一些javascript API来操作这个结构体,当然这些API是W3C标准化过的。在W3C标准公布前,Netscape 4和IE 4 就已经编写了相似的API;Mozilla根据W3C标准重写了API,只有那些在W3C中没有定义的API,Mozilla才将其保留了下来。

存取单元

To retrieve an element reference using the cross-browser approach, you use document.getElementById(aID), which works in Internet Explorer 5.0+, Mozilla-based browsers, other W3C-compliant browsers and is part of the DOM Level 1 specification.

为通过跨浏览器途径检索单元引用,你可以使用document.getElementById(aID),它是DOM Level 1 规范的一部分,并在Internet Explorer 5.0+,基于Mozilla的浏览器,以及其它适用W3C标准的浏览器中起作用。

Mozilla does not support accessing an element through document.elementName or even through the element's name, which Internet Explorer does (also called global namespace polluting). Mozilla also does not support the Netscape 4 document.layers method and Internet Explorer's document.all. While document.getElementById lets you retrieve one element, you can also use document.layers and document.all to obtain a list of all document elements with a certain tag name, such as all <div> elements.

Mozilla不支持通过document.elementName抑或通过单元名称存取单元,而Internet Explorer 支持(也被称为全球名称空间污染)。Mozilla也不支持Netscape 4 document.layers方法和Internet Explorer的document.all.。在通过document.getElementById索引单元的同时,你也可以使用document.layersdocument.all以获取带有特定标签名的所有文件单元列表,例如所有<div> 单元。

The W3C DOM Level 1 method gets references to all elements with the same tag name through getElementsByTagName(). The method returns an array in JavaScript, and can be called on the document element or other nodes to search only their subtree. To get an array of all elements in the DOM tree, you can use getElementsByTagName("*").

W3C DOM Level 1 程序通过getElementsByTagName()获取对所有标签名相同单元的索引。这种程序以Java脚本返回一个数组,并可被 document单元或其它节点访问以查找它们自己的子树。你可以使用getElementsByTagName("*")以获取DOM树中所有单元的阵列。

The DOM Level 1 methods, as shown in Table 1, are commonly used to move an element to a certain position and toggle its visibility (menus, animations). Netscape 4 used the <layer> tag, which Mozilla does not support, as an HTML element that can be positioned anywhere. In Mozilla, you can position any element using the <div> tag, which Internet Explorer uses as well and which you'll find in the HTML specification.

DOM Level 1 程序(见表1)通常被用来移动单元到一个特定的位置并切换它的可视度(菜单,动画等)。Netscape 4 用Mozilla不支持的<layer>标签作为可被任意放置的HTML单元。在Mozilla中,你可以使用<div>标签来放置任何单元,正如你在HTML规范中所见,它也同样被Internet Explorer 使用。

表1. 存取单元的程序
程序 描述
document.getElementById( aId ) 对指定ID的单元返回索引。
document.getElementsByTagName( aTagName ) 对指定文档中名称的单元返回数组。

跨越DOM

Mozilla supports the W3C DOM APIs for traversing the DOM tree through JavaScript (see Table 2). The APIs exist for each node in the document and allow walking the tree in any direction. Internet Explorer supports these APIs as well, but it also supports its legacy APIs for walking a DOM tree, such as the children property.

为通过Java脚本跨越DOM树型,Mozilla支持W3C DOM的应用编程接口(API) (见表2)。这种API存在于每一个文档节点中,并允许在树形中沿任意方向行走。Internet Explorer同样支持这些API,不过它也支持自己继承的API以进行树形行走,例如children属性。

表2. 跨越DOM的程序
属性/程序 描述
childNodes Returns an array of all child nodes of the element.返回单元中所有子节点的数组。
firstChild Returns the first child node of the element.返回单元中第一个子节点。
getAttribute( aAttributeName ) Returns the value for the specified attribute.返回指定属性的值。
hasAttribute( aAttributeName ) Returns a boolean stating if the current node has an attribute defined with the specified name.若当前节点有定义为指定名称的属性则返回布尔状态。
hasChildNodes() Returns a boolean stating whether the current node has any child nodes.无论当前节点有无子节点,返回布尔状态。
lastChild Returns the last child node of the element.返回单元中最后一个子节点。
nextSibling Returns the node immediately following the current one.返回紧接当前的节点。
nodeName Returns the name of the current node as a string.以字符串形式返回当前节点的名称。
nodeType Returns the type of the current node.返回当前节点的类型。
描述
1 Element Node 单元节点
2 Attribute Node 属性节点
3 Text Node 文本节点
4 CDATA Section Node CDATA选择节点
5 Entity Reference Node 实体索引节点
6 Entity Node 实体节点
7 Processing Instruction Node 进程中的指示节点
8 Comment Node 注释节点
9 Document Node 文档节点
10 Document Type Node 文档类型节点
11 Document Fragment Node 文档碎片节点
12 Notation Node 符号节点
nodeValue Returns the value of the current node. For nodes that contain text, such as text and comment nodes, it will return their string value. For attribute nodes, the attribute value is returned. For all other nodes, null is returned.

返回当前节点的值。对包含文本的节点,例如文本节点和注释节点,将返回它们的字符串值。对属性节点则返回属性值。对其它所有节点返回null

ownerDocument Returns the document object containing the current node.返回包含当前节点的document对象。
parentNode Returns the parent node of the current node.返回当前节点的母节点。
previousSibling Returns the node immediately preceding the current one.返回当前节点的前一个节点。
removeAttribute( aName ) Removes the specified attribute from the current node.移除当前节点中的指定属性。
setAttribute( aName, aValue ) Sets the value of the specified attribute with the specified value.将指定属性设置为指定值。

Internet Explorer has a nonstandard quirk, where many of these APIs will skip white space text nodes that are generated, for example, by new line characters. Mozilla will not skip these, so sometimes you need to distinguish these nodes. Every node has a nodeType property specifying the node type. For example, an element node has type 1, while a text node has type 3 and a comment node is type 8. The best way to only process element nodes is to iterate over all child nodes and only process those with a nodeType of 1:

Internet Explorer有个非标准的例外,即许多这些API会跳过生成的白色空格文本节点(到新一行的字符,比方说)。Mozilla则不会跳过,所以有时你需要分清这些节点。每个节点都有一个nodeType属性,标明了节点的类型,例如,单元节点是1型,而一个文本节点是3型,注释节点是8型。只处理单元节点的最好方法就是循环所有子节点而唯独处理其中1型的:

HTML: 
  <div id="foo">
    <span>Test</span>
  </div>

JavaScript: 
  var myDiv = document.getElementById("foo"); 
  var myChildren = myXMLDoc.childNodes; 
  for (var i = 0; i < myChildren.length; i++) { 
    if (myChildren[i].nodeType == 1){ 
      // element node
    };
  };

产生和操控内容

Mozilla supports the legacy methods for adding content into the DOM dynamically, such as document.write, document.open and document.close. Mozilla also supports Internet Explorer's innerHTML method, which it can call on almost any node. It does not, however, support outerHTML (which adds markup around an element, and has no standard equivalent) and innerText (which sets the text value of the node, and which you can achieve in Mozilla by using textContent).

Mozilla支持动态添加内容进DOM的旧式程序,例如document.writedocument.opendocument.close。Mozilla也支持Internet Explorer的innerHTML程序,它可以访问几乎所有节点。然而它并不支持outerHTML (添加一个单元的置标,且没有标准的等价程序)和innerText(设置节点的文本值,这可以用Mozilla中的textContent)来完成)。

Internet Explorer has several content manipulation methods that are nonstandard and unsupported in Mozilla, including retrieving the value, inserting text and inserting elements adjacent to a node, such as getAdjacentElement and insertAdjacentHTML. Table 3 shows how the W3C standard and Mozilla manipulate content, all of which are methods of any DOM node.

Internet Explorer有几个在Mozilla中不标准、不被支持的内容操控程序,包括取回数值,在节点附近添加文本和单元,例如getAdjacentElementinsertAdjacentHTML。表3显示了W3C标准和Mozilla是如何操控内容的,它们都是任意DOM节点的程序。

表3. Mozilla操控内容的程序
程序 描述
appendChild( aNode ) Creates a new child node. Returns a reference to the new child node.创建一个新节点。返回此新节点的索引。
cloneNode( aDeep ) Makes a copy of the node it is called on and returns the copy. If aDeep is true, it copies over the node's entire subtree.对被访问的节点制作备份并返回此备份。如果aDeep为真,则复制节点的整个子树。
createElement( aTagName ) Creates and returns a new and parentless DOM node of the type specified by aTagName.以aTagName指定的数值创建并返回一个新的、无母节点的DOM节点。
createTextNode( aTextValue ) Creates and returns a new and parentless DOM textnode with the data value specified by aTextValue.以aTextValue指定的数据值创建并返回一个新的、无母节点的DOM文本节点。
insertBefore( aNewNode, aChildNode ) Inserts aNewNode before aChildNode , which must be a child of the current node.将aNewNode插入到aChildNode前(aChildNode(必须是当前节点的子节点)。
removeChild( aChildNode ) Removes aChildNode and returns a reference to it.移除aChildNode并返回它的索引。
replaceChild( aNewNode, aChildNode ) Replaces aChildNode with aNewNode and returns a reference to the removed node.以aNewNode替换aChildNode并返回被移除节点的索引。

5.4Document fragments \ 文档片断

For performance reasons, you can create documents in memory, rather than working on the existing document's DOM. DOM Level 1 Core introduced document fragments, which are lightweight documents that contain a subset of a normal document's interfaces. For example, getElementById does not exist, but appendChild does. You can also easily add document fragments to existing documents.

Mozilla creates document fragments through document.createDocumentFragment(), which returns an empty document fragment.

Internet Explorer's implementation of document fragments, however, does not comply with the W3C web standards and simply returns a regular document.

出于性能的考虑,用户可以在内存中创建documents,而不使用已存在的文档的DOM。DOM第一级(Level 1)的核心引入了document fragments,一个包含部分document接口的轻量级documents。比如,有appendChild()而没有 getElementById()。读者也可以很方便的把document fragments添加到已存在的documents中。

Mozilla创建document fragments时调用document.createDocumentFragment(),它返回空的document fragment。

IE中document fragments的实现没有遵照W3C的标准,只是简单地返回普通的document。

译者注:document fragments和document是变量类型,故不翻译。

JavaScript differences \ JavaScript中的差异

Most differences between Mozilla and Internet Explorer are usually blamed on JavaScript. However, the issues usually lie in the APIs that a browser exposes to JavaScript, such as the DOM hooks. The two browsers possess few core JavaScript differences; issues encountered are often timing related.

Mozilla与IE的差别之中,常常被责备的是JavaScript。然而,问题在于浏览器提供给JavaScript的API,比如DOM hook。两个浏览器的核心JavaScript存在一些差异;常常涉及有关时间消耗的问题。

JavaScript date 的差异

The only Date difference is the getYear method. Per the ECMAScript specification (which is the specification JavaScript follows), the method is not Y2k-compliant, and running new Date().getYear() in 2004 will return "104". Per the ECMAScript specification, getYear returns the year minus 1900, originally meant to return "98" for 1998. getYear was deprecated in ECMAScript Version 3 and replaced with getFullYear(). Internet Explorer changed getYear() to work like getFullYear() and make it Y2k-compliant, while Mozilla kept the standard behavior.

关于Date的唯一差异是getYear函数。根据ECMAScript的定义(JavaScript遵从这个定义),这个函数不是Y2k兼容的,在 2004年运行new Date().getYear()会返回“104”。根据ECMAScript的定义,getYear的返回值等于年份减去1900,例如“98”是 1998的返回值。getYear在ECMAScript第3版中被getFullYear()替代。IE修改了getYear(),工作方式和 getFullYear()相似,从而使其兼容Y2K,但是Mozilla仍保持标准的方式。

JavaScript execution differences \ 运行JavaScript时的差异

Different browsers execute JavaScript differently. For example, the following code assumes that the div node already exists in the DOM by the time the script block executes:

不同的浏览器运行JavaScript时也不相同。比如,下面的代码假设在script块执行之前,节点div已经存于与DOM中:

...
<div id="foo">Loading...</div>

<script> 
  document.getElementById("foo").innerHTML = "Done."; 
</script> 

However, this is not guaranteed. To be sure that all elements exist, you should use the onload event handler on the <body> tag:

然而,这是没有保证的。要确保所有的元素都存在,用户应该在<body>标签中使用onload事件句柄(onload event handler)。

<body onload="doFinish();"> 

<div id="foo">Loading...</div> 

<script> 
  function doFinish() { 
    var element = document.getElementById("foo");
    element.innerHTML = "Done."; 
  }
</script> 
... 

Such timing-related issues are also hardware-related -- slower systems can reveal bugs that faster systems hide. One concrete example is window.open, which opens a new window:

像这些和时间耗费相关的话题也是和硬件相关的--较慢的系统可以揭示出较快的系统中隐藏的bug。举个具体的例子,window.open,它的功能是打开一个新的窗口:

<script> 
  function doOpenWindow(){ 
    var myWindow = window.open("about:blank"); 
    myWindow.location.href = "http://www.ibm.com"; 
  }
</script> 

The problem with the code is that window.open is asynchronous -- it does not block the JavaScript execution until the window has finished loading. Therefore, you may execute the line after the window.open line before the new window has finished. You can deal with this by having an onload handler in the new window and then call back into the opener window (using window.opener).

这段代码的问题在于,window.open是异步执行的--它在这个窗体加载完成之前不会阻塞JavaScript的执行。因此, window.open之后的代码有可能在新窗体加载完之前执行。用户可以用下面的方法解决这个问题:在新窗体中定义一个onload handler,然后返回到父窗体(使用window.opener)。

Differences in JavaScript-generating HTML \ JavaScript生成HTML代码的差异

JavaScript can, through document.write, generate HTML on the fly from a string. The main issue here is when JavaScript, embedded inside an HTML document (thus, inside an <script> tag), generates HTML that contains a <script> tag. If the document is in strict rendering mode, it will parse the </script> inside the string as the closing tag for the enclosing <script>. The following code illustrates this best:

通过document.write,JavaScript可以生成任意的HTML代码。这里的主要问题是,当JavaScript嵌在HTML文档(在 <script>标签中)中,生成的HTML代码中包含<script>会怎么样?如果文档(document)是strict rendering mode(严格的绘制模式),它会把字符串中的</script>当作与<script>对应的结束标签解析。下面的代码很好地说明了这种情况:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
... 
<script> 
  document.write("<script type='text\/javascript'>alert('Hello');<\/script>") 
</script> 

Since the page is in strict mode, Mozilla's parser will see the first <script> and parse until it finds a closing tag for it, which would be the first </script>. This is because the parser has no knowledge about JavaScript (or any other language) when in strict mode. In quirks mode, the parser is aware of JavaScript when parsing (which slows it down). Internet Explorer is always in quirks mode, as it does not support true XHTML. To make this work in strict mode in Mozilla, separate the string into two parts:

因为页面处于strict mode,Mozella的解析器读到第一个<script>,然后继续解析直到找到它的结束标签,那就是第一个</script>。这是因为在strict mode下,解析器不懂得关于JavaScript(或者其他语言)的任何知识。quirks mode下,解析器在解析时会考虑JavaScript(这会使它变慢)。IE一直在quirks mode,因此它不支持真正地XHTML。为了让类似地代码可以在Mozilla地strict mode下工作,把那个字符串拆成两部分就可以了:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
... 
<script> 
  document.write("<script type='text\/javascript'>alert('Hello');</" + "script>") 
</script> 

Debug JavaScript \ 调试JavaScript

Mozilla provides several ways to debug JavaScript-related issues found in applications created for Internet Explorer. The first tool is the built-in JavaScript console, shown in Figure 1, where errors and warnings are logged. You can access it in Mozilla by going to Tools -> Web Development -> JavaScript Console or in Firefox (the standalone browser product from Mozilla) at Tools -> JavaScript Console.

Mozilla提供了几种方法,用于调试原本为IE编写的程序中与JavaScript相关的问题。第一个工具是Mozilla自带的 JavaScript console(见图1),在那里记录了错误(errors)和警告(warning)。要打开它,在Mozilla中,点击Tools -> Web Development -> JavaScript Console;在firefox中(卓越的Mozilla浏览器),点击 Tools -> JavaScript Console(译注:firefox2.0中是Tools->Error Console)。

Figure 1. JavaScript console

Javascript Console

The JavaScript console can show the full log list or just errors, warnings, and messages. The error message in Figure 1 says that at aol.com, line 95 tries to access an undefined variable called is_ns70. Clicking on the link will open Mozilla's internal view source window with the offending line highlighted.

JavaScript console(或者Erroe console)可以显示完整的记录,或者只是错误、警告、信息 (errors, warnings, and messages)。图1中的错误信息说,在aol.com,95行试图去访问一个没有定义的变量is_ns70(at aol.com, line 95 tries to access an undefined variable called is_ns70)。单击该链接会打开Mozilla自带的源码查看窗口,高亮显示对应的代码行。 The console also allows you to evaluate JavaScript. To evaluate the entered JavaScript syntax, type in 1+1 into the input field and press Evaluate, as Figure 2 shows.

在console中也可以计算JavaScript表达式的值。要计算JavaScript表达式,在输入框中输入1+1然后点击Evaluate(计算),如图2所示。

Figure 2. JavaScript console evaluating

JavaScript Console evaluating

Mozilla's JavaScript engine has built-in support for debugging, and thus can provide powerful tools for JavaScript developers. Venkman, shown in Figure 3, is a powerful, cross-platform JavaScript debugger that integrates with Mozilla. It is usually bundled with Mozilla releases; you can find it at Tools -> Web Development -> JavaScript Debugger. For Firefox, the debugger isn't bundled; instead, you can download and install it from the Venkman Project Page. You can also find tutorials at the development page, located at the Venkman Development Page.

Mozilla的JavaScript引擎内建了调试功能,这样就提供为JavaScript编写者提供了强有力的工具。图3中的Venkman,与 Mozilla集成,是一个功能强大、跨平台的JavaScript调试工具。它通常包含Mozilla的发行版本中,用户可以点击 Tools -> Web Development -> JavaScript Debugger找到它。对于Firefox,这个调试工具不是集成的;用户可以从Venkman Project Page下载并安装它。用户也会可以在Venkman Development Page找到用户指南。 Figure 3. Mozilla's JavaScript debugger

Mozilla's JavaScript debugger

The JavaScript debugger can debug JavaScript running in the Mozilla browser window. It supports such standard debugging features as breakpoint management, call stack inspection, and variable/object inspection. All features are accessible through the user interface or through the debugger's interactive console. With the console, you can execute arbitrary JavaScript in the same scope as the JavaScript currently being debugged.

这个JavaScript调试工具可以调试正在Mozilla浏览器窗口中运行的JavaScript代码。它支持标准的调试功能,像断点管理、查看堆栈、查看变量/对象的值等。所有的调试功能,都可以通过界面或调试工具的命令行被用户使用。在JavaScript代码的调试过程中,只要处于同一个作用域,用户就可以通过命令行运行任意的JavaScript代码。

CSS 的差异

Mozilla-based products have the strongest support for Cascading Style Sheets (CSS), including most of CSS1, CSS2.1 and parts of CSS3, compared to Internet Explorer as well as all other browsers.

与IE以及其他浏览器相比,基于Mozilla的产品对层叠样式表(CSS)提供了最好的支持,包括CSS1、CSS2的绝大部分和CSS3的一部分。

For most issues mentioned below, Mozilla will add an error or warning entry into the JavaScript console. Check the JavaScript console if you encounter CSS-related issues.

对于下文提到的很多问题,Mozilla会在JavaScript console中显示出error或warning项。如果用户碰到CSS方面的问题,可以去看看JavaScript console。

Mimetypes (when CSS files are not applied)/ mimetype(何时CSS文件不适用)

The most common CSS-related issue is that CSS definitions inside referenced CSS files are not applied. This is usually due to the server sending the wrong mimetype for the CSS file. The CSS specification states that CSS files should be served with the text/css mimetype. Mozilla will respect this and only load CSS files with that mimetype if the Web page is in strict standards mode. Internet Explorer will always load the CSS file, no matter with which mimetype it is served. Web pages are considered in strict standards mode when they start with a strict doctype. To solve this problem, you can make the server send the right mimetype or remove the doctype. I'll discuss more about doctypes in the next section.

与CSS相关的问题中,最常见的就是被引用的CSS文件中的CSS定义不适用。这个问题通常是由于服务器给CSS文件发送了错误的 mimetype。CSS的规范中指出,CSS文件的mimetype应该为text/css。如果网页是strict standards mode,Mozilla会遵从这个规范,并且只有在CSS文件的mimetype是text/css时才加载该文件IE不管是那种mimetype,总 会加载CSS文件。网页只有以doctype开头,才被认为是strict standards mode。为了解决这个问题,用户可以让服务器发送正确的mimetype,或者删除doctype。在下面的章节中,我将详细的讲解doctype。

译注:mime指多用途的网际邮件扩充协议。

CSS and units/ CSS与度量单位

Many Web applications do not use units with their CSS, especially when you use JavaScript to set the CSS. Mozilla tolerates this, as long as the page is not rendered in strict mode. Since Internet Explorer does not support true XHTML, it does not care if no units are specified. If the page is in strict standards mode, and no units are used, then Mozilla ignores the style:

很多网页应用程序在它们的CSS中都不使用度量单位,尤其是用户在JavaScript中设置CSS的时候。Mozilla对此很宽容,只要网页不 是在strict mode。因为IE不支持真正的XHTML,即使没有定义度量单位它也不会关心。如果网页是strict standards mode,并且没有使用度量单位,Mozilla将忽略这些样式:

<DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 
  "http://www.w3.org/TR/html4/strict.dtd"> 
<html> 
  <head> 
   <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
   <title>CSS and units example</title> 
  </head> 
  <body> 
    // works in strict mode 
    <div style="width: 40px; border: 1px solid black;">
      Text
    </div>

    // will fail in strict mode 
    <div style="width: 40; border: 1px solid black;">
      Text
    </div>
  </body> 
</html> 

Since the above example has a strict doctype, the page is rendered in strict standards mode. The first div will have a width of 40px, since it uses units, but the second div won't get a width, and thus will default to 100% width. The same would apply if the width were set through JavaScript.

上面的例子中有明确的doctype定义,所以该网页以 strict standards mode显示。(在显示的结果中)由于第一个div中使用了度量单位,所以它的宽度是40象素;但第二个div没有获取width的值,因此它的 width的值是默认的100%(译注:在firefox2.0中,默认值是40px)。如果width属性是通过JavaScript设置的,同样的事 也会发生。

JavaScript 与 CSS

Since Mozilla supports the CSS standards, it also supports the CSS DOM standard for setting CSS through JavaScript. You can access, remove, and change an element's CSS rules through the element's style member:

因为Mozilla支持CSS标准,所以它也支持CSS DOM标准,可以通过JavaScript设置CSS。用户可以通过元素的style成员读取、修改或删除元素的CSS规则:

<div id="myDiv" style="border: 1px solid black;">
  Text
</div>

<script>
  var myElm = document.getElementById("myDiv"); 
  myElm.style.width = "40px"; 
</script>

You can reach every CSS attribute that way. Again, if the Web page is in strict mode, you must set a unit or else Mozilla will ignore the command. When you query a value, say through .style.width, in Mozilla and Internet Explorer, the returned value will contain the unit, meaning a string is returned. You can convert the string into a number through parseFloat("40px").

用户可以用同样的方法访问所有的CSS属性。再次提醒,如果网页是strict mode,用户必须设置度量单位,否则Mozilla将忽略这行代码。用户可以用 .style.width在Mozilla和IE中查询属性值,返回值是包含度量单位在内的,也就是说返回值是string(字符串)。用户可以用parseFloat("40px")把string转换成数字。

CSS 溢出(overflow) 的差异

CSS added the notion of overflow, which allows you to define how to handle overflow; for example, when the contents of a div with a specified height are taller than that height. The CSS standard defines that if no overflow behavior is set in this case, the div contents will overflow. However, Internet Explorer does not comply with this and will expand the div beyond its set height in order to hold the contents. Below is an example that shows this difference:

CSS中有overfolw(溢出)的标记,有了它,开发者可以自己决定如何处理overflow;比如,div的内容的实际高度比div定义的高 度高。CSS标准中的定义是,如果这种情况下没有设置overflow的处理代码,div的内容将溢出。然而,IE并不遵从这个定义,它为了显示全部内 容,会拉长这个div,超出原来设置的高度。下面的例子可以说明这点差异:

<div style="height: 100px; border: 1px solid black;">
  <div style="height: 150px; border: 1px solid red; margin: 10px;">
    a
  </div>
</div>

As you can see in Figure 4, Mozilla acts like the W3C standard specifies. The W3C standard says that, in this case, the inner div overflows to the bottom since the inner content is taller than its parent. If you prefer the Internet Explorer behavior, simply do not specify a height on the outer element.

如图4所示,Mozilla按照W3C的规范处理。W3C标准说,在这种情况下,因为内div(里面的那个div)的内容高于外div,所以内div会溢出底部。如果用户喜欢IE的行为,在外div中不定义高度就可以了。

Figure 4. DIV overflow

DIV Overflow

hover 的差异

The nonstandard CSS hover behavior in Internet Explorer occurs on quite a few web sites. It usually manifests itself by changing text style when hovered over in Mozilla, but not in Internet Explorer. This is because the a:hover CSS selector in Internet Explorer matches <a href="">...</a> but not <a name="">...</a>, which sets anchors in HTML. The text changes occur because authors encapsulate the areas with the anchor-setting markup:

在IE中,非标准的CSS hover行为只有在少数页面中才会发生。在Mozilla中,CSS hover一般会在(鼠标)掠过其上方时,改变颜色秀出自己,但在IE中不会。这是因为IE中a:hover 的CSS选择器匹配<a href="">...</a>,但不匹配<a name="">...</a>,后者是在HTML中设置anchor(锚点或锚记)。文本发生改变是因为作者用设置anchor的标记把这个区域包围了起来:

CSS:
  a:hover {color: green;}

HTML:
  <a href="foo.com">This text should turn green when you hover over it.</a>

  <a name="anchor-name">
    This text should change color when hovered over, but doesn't
    in Internet Explorer.
  </a>

Mozilla follows the CSS specification correctly and will change the color to green in this example. You can use two ways to make Mozilla behave like Internet Explorer and not change the color of the text when hovered over:

  • First, you can change the CSS rule to be a:link:hover {color: green;}, which will only change the color if the element is a link (has an href attribute).
  • Alternatively, you can change the markup and close the opened <a /> before the start of the text -- the anchor will continue to work this way.

Mozilla完全遵从CSS的规范,在本例中会把颜色变成绿色。用户有两种办法,可以让Mozilla像IE一样,在鼠标掠过这段文字时不改变颜色:

   * 一、用户可以把CSS规则改为 a:link:hover {color: green;},这样,只有元素是超链接时(有href属性),颜色才会改变。
   * 二、用户可以改变标记,在文字开始前结束<a />--这样anchor可以保留原有的功能。

Quirks versus standards mode/ 另类模式vs标准模式

Older legacy browsers, such as Internet Explorer 4, rendered with so-called quirks under certain conditions. While Mozilla aims to be a standards-compliant browser, it has three modes that support older Web pages created with these quirky behaviors. The page's content and delivery determine which mode Mozilla will use. Mozilla will indicate the rendering mode in View -> Page Info (or Ctrl+I) ; Firefox will list the rendering mode in Tools -> Page Info. The mode in which a page is located depends on its doctype.

较老的浏览器,如IE4,在一些特定的情况下,会用所谓的另类模式(quirks)显示页面。因为Mozilla的目标是一款支持标准的浏览器,所以它有三种模式,可以支持带有特有行为的老网页。页面的内容以及delvery决定着Mozilla使用那种模式。Mozilla可以用View -> Page Info (或 Ctrl+I)指示显示模式;Firefox用Tools -> Page Info列出显示模式。页面处于哪种模式由doctype(文档类型声明)决定。

Doctypes (short for document type declarations) look like this:

Doctype(document type declarations的缩写)如下所示:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

The section in blue is called the public identifier, the green part is the system identifier, which is a URI.

蓝色的部分是公有标识符;绿色的部分是系统标识符,它是个URI。

标准模式

Standards mode is the strictest rendering mode -- it will render pages per the W3C HTML and CSS specifications and will not support any quirks. Mozilla uses it for the following conditions:

标准模式(standard mode)是最严格的显示模式——它将根据W3C HTML和CSS规范显示页面,而不支持任何特有行为。Mozilla在下面这些情况中使用该模式:

  • If a page is sent with a text/xml mimetype or any other XML or XHTML mimetype
  • For any "DOCTYPE HTML SYSTEM" doctype (for example, <!DOCTYPE HTML SYSTEM "http://www.w3.org/TR/REC-html40/strict.dtd">), except for the IBM doctype
  • For unknown doctypes or doctypes without DTDs
  1. 如果页面含有text/xml的mimetype,或者其他的XML以及XHTML的mimetype
  2. 如果doctype是 "DOCTYPE HTML SYSTEM" (例如, <!DOCTYPE HTML SYSTEM "http://www.w3.org/TR/REC-html40/strict.dtd">),但不包括IBM doctype
  3. 如果doctype未知,或doctype中没有DTD

准标准模式

Mozilla introduced almost standards mode for one reason: a section in the CSS 2 specification breaks designs based on a precise layout of small images in table cells. Instead of forming one image to the user, each small image ends up with a gap next to it. The old IBM homepage shown in Figure 5 offers an example.

Mozilla引入了准标准模式(almost standards mode)是因为以下原因:CSS2规范中的一节破坏了基于表格的小图片精确布局的设计。不同于合成一张图片给用户,每张小图片之后都有一小段间隙。图5中的IBM旧首页就是一个例子。

图5. 图片间隙

Image Gap

Almost standards mode behaves almost exactly as standards mode, except when it comes to an image gap issue. The issue occurs often on standards-compliant pages and causes them to display incorrectly.

准标准模式的行为与标准模式极为接近,除了它碰到图片后有间隙的时候。这种情况常常在兼容标准的页面中发生,使页面显示不正确。

Mozilla uses almost standards mode for the following conditions:

在下面这些情况下中Mozilla使用准标准模式:

  • 对于所有的“宽松的”dictype (例如, <!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN">, <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">)
  • 对于IBM doctype (<!DOCTYPE html SYSTEM "http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd">)

You can read more about the image gap issue.

读者可以阅读更多关于 图片间隙的话题

另类(quirk)模式

Currently, the Web is full of invalid HTML markup, as well as markup that only functions due to bugs in browsers. The old Netscape browsers, when they were the market leaders, had bugs. When Internet Explorer arrived, it mimicked those bugs in order to work with the content at that time. As newer browsers came to market, most of these original bugs, usually called quirks, were kept for backwards compatibility. Mozilla supports many of these in its quirks rendering mode. Note that due to these quirks, pages will render slower than if they were fully standards-compliant. Most Web pages are rendered under this mode.

当前,互联网上有很多错误的HTML标记,也包括只有因为浏览器的bug才能起作用的标记。老版本的Netscape浏览器——当时市场的主流——是有bug的。当IE成为市场主流的时候,为了在当时能处理那些页面,它模仿了这些bug。当新的浏览器面世的时候,原来的大多数bug——通常被称作quirks——为了兼容性而被保留了下来。Mozilla在另类显示模式中支持很多这种页面。注意,由于这些“另类”,页面显示的速度比它们是标准页面时要慢。大多数网页都是以这种模式显示的。

Mozilla uses quirks mode for the following conditions:

在以下情况中,Mozilla使用另类模式:

  • 没有定义doctype
  • doctype没有系统标识符(比如, <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">)

For further reading, check out: Mozilla Quirks Mode Behavior and Mozilla's DOCTYPE sniffing.

要想了解更多,请阅读 Mozilla Quirks Mode BehaviorMozilla's DOCTYPE sniffing

事件差异

Mozilla and Internet Explorer are almost completely different in the area of events. The Mozilla event model follows the W3C and Netscape model. In Internet Explorer, if a function is called from an event, it can access the event object through window.event. Mozilla passes an event object to event handlers. They must specifically pass the object on to the function called through an argument. A cross-browser event handling example follows:

在事件(event)处理方面,可以说Mozilla与IE是完全不同。Mozilla的事件处理模型沿用了W3C和Netscape的模型。在IE中,如果函数被一个事件调用,它可以通过window.event访问event对象。而Mozilla把event对象传递给事件句柄(event handler)。它们必须用不同的参数把这个对象传递到函数中。跨浏览器的事件处理代码可能会写成这样:

<div onclick="handleEvent(event);">Click me!</div>

<script>
  function handleEvent(aEvent) { 
    // if aEvent is null, means the Internet Explorer event model, 
    // so get window.event. 
    var myEvent = aEvent ? aEvent : window.event; 
  }
</script>

Sometimes this doesn't work because Internet Explorer "catches" the aEvent parameter, identifiying it as not null, making it not use window.event any longer. The solution is to simply test for the window.event property:

但有时候这不会起作用,因为IE“捕获”这个aEvent参数,认为它不是空值,这样就使得window.event不会被用到。其实简单的解决办法是判断下window.event属性:

<div onclick="handleEvent(event);">Click me!</div>

<script>
  function handleEvent(aEvent) { 
    var myEvent = window.event ? window.event : aEvent;
  }
</script>

The properties and functions that the event object exposes are also often named differently between Mozilla and Internet Explorer, as Table 4 shows.

Mozilla与IE中,事件属性和函数的名字通常是不一样的,如表4所示:

表4 Mozilla与IE之间的事件属性差异
Internet Explorer Name Mozilla Name Description
altKey altKey Boolean property that returns whether the alt key was pressed during the event.
cancelBubble stopPropagation() Used to stop the event from bubbling farther up the tree.
clientX clientX The X coordinate of the event, in relation to the element viewport.
clientY clientY The Y coordinate of the event, in relation to the element viewport.
ctrlKey ctrlKey Boolean property that returns whether the Ctrl key was pressed during the event.
fromElement relatedTarget For mouse events, this is the element from which the mouse moved away.
keyCode keyCode For keyboard events, this is a number representing the key that was pressed. It is 0 for mouse events.
returnValue preventDefault() Used to prevent the event's default action from occurring.
screenX screenX The X coordinate of the event, in relation to the screen.
screenY screenY The Y coordinate of the event, in relation to the screen.
shiftKey shiftKey Boolean property that returns whether the Shift key was pressed during the event.
srcElement target The element to which the event was originally dispatched.
toElement currentTarget For mouse events, this is the element to which the mouse moved.
type type Returns the name of the event.

关联事件处理函数

Mozilla supports two ways to attach events through JavaScript. The first, supported by all browsers, sets event properties directly on objects. To set a click event handler, a function reference is passed to the object's onclick property:

Mozilla有两种方法通过JavaScript添加event。第一种,也是所有浏览器都支持的,直接给对象(object)添加event属性。要设置一个click的event句柄,可以使用函数的引用设置onclick属性:

<div id="myDiv">Click me!</div>

<script>
  function handleEvent(aEvent) {
    // if aEvent is null, means the Internet Explorer event model,
    // so get window.event.
    var myEvent = aEvent ? aEvent : window.event;
  }

  function onPageLoad(){
    document.getElementById("myDiv").onclick = handleEvent;
  } 
</script>

Mozilla fully supports the W3C standard way of attaching listeners to DOM nodes. You use the addEventListener() and removeEventListener() methods, and have the benefit of being able to set multiple listeners for the same event type. Both methods require three parameters: the event type, a function reference, and a boolean denoting whether the listener should catch events in their capture phase. If the boolean is set to false, it will only catch bubbling events. W3C events have three phases: capturing, at target, and bubbling. Every event object has an eventPhase attribute indicating the phase numerically (0 indexed). Every time you trigger an event, the event starts at the DOM's outermost element, the element at the top of the DOM tree. It then walks the DOM using the most direct route toward the target, which is the capturing phase. When the event reaches the target, the event is in the target phase. After arriving at the target, it walks up the DOM tree back to the outermost node; this is bubbling. Internet Explorer's event model only has the bubbling phase; therefore, setting the third parameter to false results in Internet Explorer-like behavior:

Mozilla支持W3C标准定义的添加linstener给DOM节点的所有方法。用户可以使用addEventListener()removeEventListener() 函数,也可以向同一个event type(事件类型)添加多个listener。两个函数都需要三个参数:event type(事件类型),function reference(函数引用),和一个标识listener在捕获阶段(capture phase)是否捕获事件的boolean(布尔值)。如果boolean参数设为false,它将只捕获bubbling event。W3C对event定义了三个阶段:capturing,at target,和bubbling。每个event对象都有eventPhase属性,以数字表明所处的阶段(索引从0开始)。每当event被触发时,event从DOM最外层的元素(在DOM 树型结构最顶端的元素)开始,然后它沿着最短的路径向target(目标节点)遍历,这就是捕获阶段。当事件到达目标节点, 事件就转到目标节点阶段。到达目标节点之后,它就沿着DOM树上溯到最外层的节点;这个过程就是冒泡(bubling)。IE的事件模型(event model)只支持冒泡阶段,所以,把第三个参数设为false就会得到与IE的相似行为:

<div id="myDiv">Click me!</div> 

<script> 

  function handleEvent(aEvent) {
    // if aEvent is null, it is the Internet Explorer event model,
    // so get window.event.
    var myEvent = aEvent ? aEvent : window.event;
  }

  function onPageLoad() {
    var element = document.getElementById("myDiv");
    element.addEventListener("click", handleEvent, false);
  }
</script>

One advantage of addEventListener() and removeEventListener() over setting properties is that you can have multiple event listeners for the same event, each calling another function. Thus, to remove an event listener requires all three parameters be the same as the ones you use when adding the listener.

和设置属性相比,addEventListener()和removeEventListener()的优势在于,对同一个event可以有多个 event listener,每一个都是调用不同的函数。因此,删除一个event listener时,要求三个参数与添加listener时的三个参数完全相同。

Mozilla does not support Internet Explorer's method of converting <script> tags into event handlers, which extends <script> with for and event attributes (see Table 5). It also does not support the attachEvent and detachEvent methods. Instead, you should use the addEventListener and removeEventListener methods. Internet Explorer does not support the W3C events specification.

Mozilla不支持IE中把<script>标签转换为event handler的方法——IE用for和event属性对<script>进行了扩展(参加表5)。它用样不支持attachEvent和 detachEvent方法。用户应该使用addEventListener和removeEventListener方法。IE不支持W3C的 event规范。

表5 Mozilla与IE之间事件方法的差异
Internet Explorer 方法 Mozilla 方法 描述
attachEvent(aEventType, aFunctionReference) addEventListener(aEventType, aFunctionReference, aUseCapture) Adds an event listener to a DOM element.
detachEvent(aEventType, aFunctionReference) removeEventListener(aEventType, aFunctionReference, aUseCapture) Removes an event listener to a DOM element.

富文本编辑

While Mozilla prides itself with being the most W3C web standards compliant browser, it does support nonstandard functionality, such as innerHTML and rich text editing, if no W3C equivalent exists.

在Mozilla作为对W3C web标准支持最好的浏览器的同时,它也支持非标准的功能,比如innerHTML 和富文本编辑rich text editing, 前提是没有相应的W3C规范。

Mozilla 1.3 introduced an implementation of Internet Explorer's designMode feature, which turns an HTML document into a rich text editor field. Once turned into the editor, commands can run on the document through the execCommand command. Mozilla does not support Internet Explorer's contentEditable attribute for making any widget editable. You can use an iframe to add a rich text editor.

Mozilla1.3引入了IE中designMode功能,它可以把HTML文档转换为富文本编辑区域 ,各种指令可以通过execCommand命令在document中执行。Mozilla不支持IE中把所有控件都变为可编辑状态(editable)的contentEditable属性。但用户可以用iframe添加富文本编辑。

富文本差异

Mozilla supports the W3C standard of accessing iframe's document object through IFrameElmRef.contentDocument, while Internet Explorer requires you to access it through document.frames["IframeName"] and then access the resulting document:

Mozilla支持通过IFrameElmRef.contentDocument访问iframe的document对象的W3C标准;而IE要求用户通过document.frames["IframeName"]获取它,再访问结果中的document

<script>
function getIFrameDocument(aID) {
  var rv = null; 

  // if contentDocument exists, W3C compliant (Mozilla)
  if (document.getElementById(aID).contentDocument){
    rv = document.getElementById(aID).contentDocument;
  } else {
    // IE
    rv = document.frames[aID].document;
  }
  return rv;
}
</script> 

Another difference between Mozilla and Internet Explorer is the HTML that the rich text editor creates. Mozilla defaults to using CSS for the generated markup. However, Mozilla allows you to toggle between HTML and CSS mode using the useCSS execCommand and toggling it between true and false. Internet Explorer always uses HTML markup.

Mozilla与IE间的另一个差别是富文本编辑生成的HTML不同。 Mozilla默认使用CSS标记。当然,Mozilla也允许用户在execCommand中用useCSS进行HTML与CSS模式的切换。而IE只使用HTML标记。

Mozilla (CSS): 
  <span style="color: blue;">Big Blue</span> 

Mozilla (HTML): 
  <font color="blue">Big Blue</font> 

Internet Explorer: 
  <FONT color="blue">Big Blue</FONT> 

Below is a list of commands that execCommand in Mozilla supports:

下面是Mozilla支持的execCommand命令的列表:

Table 6. Rich text editing commands
Command Name Description Argument
bold Toggles the selection's bold attribute. ---
createlink Generates an HTML link from the selected text. The URL to use for the link
delete Deletes the selection. ---
fontname Changes the font used in the selected text. The font name to use (Arial, for example)
fontsize Changes the font size used in the selected text. The font size to use
fontcolor Changes the font color used in the selected text. The color to use
indent Indents the block where the caret is. ---
inserthorizontalrule Inserts an <hr> element at the cursor's position. ---
insertimage Inserts an image at the cursor's position. URL of the image to use
insertorderedlist Inserts an ordered list (<ol>) element at the cursor's position. ---
insertunorderedlist Inserts an unordered list (<ul>) element at the cursor's position. ---
italic Toggles the selection's italicize attribute. ---
justifycenter Centers the content at the current line. ---
justifyleft Justifies the content at the current line to the left. ---
justifyright Justifies the content at the current line to the right. ---
outdent Outdents the block where the caret is. ---
redo Redoes the previous undo command. ---
removeformat Removes all formatting from the selection. ---
selectall Selects everything in the rich text editor. ---
strikethrough Toggles the strikethrough of the selected text. ---
subscript Converts the current selection into subscript. ---
superscript Converts the current selection into superscript. ---
underline Toggles the underline of the selected text. ---
undo Undoes the last executed command. ---
unlink Removes all link information from the selection. ---
useCSS Toggles the usage of CSS in the generated markup. Boolean value

For more information, visit Rich-Text Editing in Mozilla.

想了解更多信息,请参见Rich-Text Editing in Mozilla

XML差异

Mozilla has strong support for XML and XML-related technologies, such as XSLT and Web services. It also supports some nonstandard Internet Explorer extensions, such as XMLHttpRequest.

Mozilla对XML以及与XML相关的技术提供强有力的支持,比如XSLT和Web services。它也支持一些非标准的IE扩展,比如XMLHttpRequest。

(tick.huang@gmail.com end @ 2006.11.8)

如何处理XML

As with standard HTML, Mozilla supports the W3C XML DOM specification, which allows you to manipulate almost any aspect of an XML document. Differences between Internet Explorer's XML DOM and Mozilla are usually caused by Internet Explorer's nonstandard behaviors. Probably the most common difference is how they handle white space text nodes. Often when XML generates, it contains white spaces between XML nodes. Internet Explorer, when using XMLNode.childNodes[], will not contain these white space nodes. In Mozilla, those nodes will be in the array.

就像支持标准的HTML一样,Mozilla同样支持W3C XML DOM的规范,这使用户可以对XML文档进行多种多样的操作。IE与Mozilla之间的XML DOM差异通常是有IE的非标准行为引起的。也许最常见的差异就是它们如何处理文本节点(译注:text node,指<.../>或<...>...</....>之外的文件内容,包括空格、回车等)的空白符(译注:空格、制表符等)。通常,生成XML时,在XML节点间会有空白符。IE调用XMLNode.childNodes[]时,在结果中不会包含这些是空白符的节点。而Mozilla中,这些空节点会在数组中。

XML: 
  <?xml version="1.0"?> 
  <myXMLdoc xmlns:myns="http://myfoo.com"> 
    <myns:foo>bar</myns:foo> 
  </myXMLdoc>

JavaScript:
  var myXMLDoc = getXMLDocument().documentElement; 
  alert(myXMLDoc.childNodes.length); 

The first line of JavaScript loads the XML document and accesses the root element (myXMLDoc) by retrieving the documentElement. The second line simply alerts the number of child nodes. Per the W3C specification, the white spaces and new lines merge into one text node if they follow each other. For Mozilla, the myXMLdoc node has three children: a text node containing a new line and two spaces; the myns:foo node; and another text node with a new line. Internet Explorer, however, does not abide by this and will return "1" for the above code, namely only the myns:foo node. Therefore, to walk the child nodes and disregard text nodes, you must distinguish such nodes.

第一行JavaScript代码加载XML document并通过documentElement获取根元素(myXMLDoc)。 第二行代码只是简单的显示子节点的个数。根据W3C规范,如果空格和回车相邻,它们将被合并成一个文本节点(text node)。对于Mozilla,myXMLdoc节点有三个子节点:第一个节点有一个回车和两个空格;第二个节点是myns:foo;第三个节点有一个 回车。而IE没有遵守这个规范,上面的这段代码将返回“1”,也就是说只有myns:foo节点。所以,遍历子节点以及是否忽略文本节点(text node),用户需要区分对待。

As mentioned earlier, every node has a nodeType attribute representing the node type. For example, an element node has type 1, while a document node has type 9. To disregard text nodes, you must check for types 3 (text node) and 8 (comment node).

在前面已经提过,每个节点有个nodeType属性标识节点的类型。比如,元素节点(element node)的类型是1,文档节点(document node)的类型是9。要忽略text node,需要判断类型3(文本节点)和8(注释节点)。

XML:
  <?xml version="1.0"?>   
  <myXMLdoc xmlns:myns="http://myfoo.com"> 
    <myns:foo>bar</myns:foo> 
  </myXMLdoc>

JavaScript: 
  var myXMLDoc = getXMLDocument().documentElement; 
  var myChildren = myXMLDoc.childNodes; 

  for (var run = 0; run < myChildren.length; run++){ 
    if ( (myChildren[run].nodeType != 3) &&
          myChildren[run].nodeType != 8) ){ 
      // 不是文本节点或注释节点
    };
  };

XML数据岛

Internet Explorer has a nonstandard feature called XML data islands, which allow you to embed XML inside an HTML document using the nonstandard HTML tag <xml>. Mozilla does not support XML data islands and handles them as unknown HTML tags. You can achieve the same functionality using XHTML; however, because Internet Explorer's support for XHTML is weak, this is usually not an option.

IE有个非标准的特性,被称为XML data islands,它允许用户在HTML文档中使用HTML的标记<xml> 嵌入XML。Mozilla不支持XML数据岛,就把它当作未知的HTML标记来处理。 用户可以使用XHTML实现相同的功能;但是,因为IE对XHTML的支持比较弱,所以通常不推荐这种方法。

One cross-browser solution is to use DOM parsers, which parse a string that contains a serialized XML document and generates the document for the parsed XML. Mozilla uses the DOMParser class, which takes the serialized string and creates an XML document out of it. In Internet Explorer, you can achieve the same functionality using ActiveX. A new Microsoft.XMLDOM generates and has a loadXML method that can take in a string and generate a document from it. The following code shows you how:

一个跨浏览器的解决办法是使用DOM解析器,它可以解析内容是序列化的(serialized)XML文档的string,然后生成文档。 Mozilla使用DOMParser类,它以序列化的string作为输入,生成XML文档。在IE中,用户可以使用ActiveX实现相同的功能。Microsoft.XMLDOM有个方法loadXML,它以string作为输入,生成文档。下面的代码演示了如何实现:

IE XML data island: 
  .. 
  <xml id="xmldataisland"> 
    <foo>bar</foo> 
  </xml>

Cross-browser solution: 
  var xmlString = "<xml id=\"xmldataisland\"><foo>bar</foo></xml>"; 

  var myDocument; 

  if (document.implementation.createDocument){ 
    // Mozilla,创建DOMParser
    var parser = new DOMParser(); 
    myDocument = parser.parseFromString(xmlString, "text/xml"); 
  } else if (window.ActiveXObject){ 
    // IE,用ActiveX创建XML document,然后把loadXML当作DOM解析器来用
    myDocument = new ActiveXObject("Microsoft.XMLDOM"); 
    myDocument.async="false"; 

    myDocument.loadXML(xmlString);
  }

XML HTTP请求

Internet Explorer allows you to send and retrieve XML files using MSXML's XMLHTTP class, which is instantiated through ActiveX using new ActiveXObject("Msxml2.XMLHTTP") or new ActiveXObject("Microsoft.XMLHTTP"). Since there is no standard method of doing this, Mozilla provides the same functionality in the global JavaScript XMLHttpRequest object. The object generates asynchronous requests by default.

IE允许用户使用MSXML的XMLHTTP类发送和接受XML文件,这个类通过调用new ActiveXObject("Msxml2.XMLHTTP")new ActiveXObject("Microsoft.XMLHTTP")进行实例化。因为不存在具有此功能的标准函数,所以Mozilla在全局的JavaScript对象XMLHttpRequest中提供了相同的功能。该对象默认生成异步的请求。

After instantiating the object using new XMLHttpRequest(), you can use the open method to specify what type of request (GET or POST) you use, which file you load, and if it is asynchronous or not. If the call is asynchronous, then give the onload member a function reference, which is called once the request has completed.

使用new XMLHttpRequest()实例化对象后,用户可以使用open 函数指定请求的类型(GET或POST)、要加载的文件、以及是否为异步调用。如果是异步调用,需要给onload成员一个函数引用,请求一完成,这个函数就会被调用。

同步请求:

  var myXMLHTTPRequest = new XMLHttpRequest(); 
  myXMLHTTPRequest.open("GET", "data.xml", false); 

  myXMLHTTPRequest.send(null); 

  var myXMLDocument = myXMLHTTPRequest.responseXML; 

异步请求:

  var myXMLHTTPRequest; 

  function xmlLoaded() { 
    var myXMLDocument = myXMLHTTPRequest.responseXML; 
  }

  function loadXML(){ 
    myXMLHTTPRequest = new XMLHttpRequest();

    myXMLHTTPRequest.open("GET", "data.xml", true);

    myXMLHTTPRequest.onload = xmlLoaded; 

    myXMLHTTPRequest.send(null); 
  }

Table 7 features a list of available methods and properties for Mozilla's XMLHttpRequest.

表7列出了Mozilla的XMLHttpRequest所有方法和属性。

Table 7. XMLHttpRequest methods and properties
Name Description
void abort() Stops the request if it is still running.
string getAllResponseHeaders() Returns all response headers as one string.
string getResponseHeader(string headerName) Returns the value of the specified header.
functionRef onerror If set, the references function will be called whenever an error occurs during the request.
functionRef onload If set, the references function will be called when the request completes successfully and the response has been received. Use when an asynchronous request is used.
void open (string HTTP_Method, string URL)

void open (string HTTP_Method, string URL, boolean async, string userName, string password)
Initializes the request for the specified URL, using either GET or POST as the HTTP method. To send the request, call the send() method after initialization. If async is false, the request is synchronous, else it defaults to asynchronous. Optionally, you can specify a username and password for the given URL needed.
int readyState State of the request. Possible values:
Value Description
0 UNINITIALIZED - open() has not been called yet.
1 LOADING - send() has not been called yet.
2 LOADED - send() has been called, headers and status are available.
3 INTERACTIVE - Downloading, responseText holds the partial data.
4 COMPLETED - Finished with all operations.
string responseText String containing the response.
DOMDocument responseXML DOM Document containing the response.
void send(variant body) Initiates the request. If body is defined, it issent as the body of the POST request. body can be an XML document or a string serialized XML document.
void setRequestHeader (string headerName, string headerValue) Sets an HTTP request header for use in the HTTP request. Has to be called after open() is called.
string status The status code of the HTTP response.

XSLT差异

Mozilla supports XSL Transformations (XSLT) 1.0. It also allows JavaScript to perform XSLT transformations and allows running XPATH on a document.

Mozilla支持XSLT 1.0( XSL Transformations)。它也允许JavaScript执行XSLT转换,和对document运行XPATH。

Mozilla requires that you send the XML and XSLT file holding the stylesheet with an XML mimetype (text/xml or application/xml). This is the most common reason why XSLT won't run in Mozilla but will in Internet Explorer. Mozilla is strict in that way.

Mozilla要求用户发送含有stylesheet的XML和XSLT文件时要有mimetype XML(text/xml or application/xml)。Mozilla对此要求很严格。这就是为什么XSLT不能在Mozilla中运行而能在IE中运行的最常见的原因。

Internet Explorer 5.0 and 5.5 supported XSLT's working draft, which is substantially different than the final 1.0 recommendation. The easiest way to distinguish what version an XSLT file was written against is to look at the namespace. The namespace for the 1.0 recommendation is http://www.w3.org/1999/XSL/Transform, while the working draft's namespace is http://www.w3.org/TR/WD-xsl. Internet Explorer 6 supports the working draft for backwards compatibility, but Mozilla does not support the working draft, only the final recommendation.

IE5.0和5.5支持XSLT的工作草案(working draft),这个工作草案和1.0最终推荐版(final 1.0 recommendation)之间有很大的差异。区分XSLT文件版本的最简单的方法是查看命名空间(namespace)。1.0推荐版的命名空间是http://www.w3.org/1999/XSL/Transform,而working draft的命名空间是http://www.w3.org/TR/WD-xsl。 IE6为了兼容性,支持工作草案;但是Mozilla不支持工作草案,它只支持最终推荐版。

If XSLT requires you to distinguish the browser, you can query the "xsl:vendor" system property. Mozilla's XSLT engine will report itself as "Transformiix" and Internet Explorer will return "Microsoft."

如果XLST要求用户区分浏览器,用户可以查询系统属性“xsl:vendor”。Mozilla的XLST引擎会报告说它自己是“transformiix”,而IE将返回“Microsoft”。

<xsl:if test="system-property('xsl:vendor') = 'Transformiix'"> 
  <!-- Mozilla specific markup --> 
</xsl:if> 
<xsl:if test="system-property('xsl:vendor') = 'Microsoft'"> 
  <!-- Internet Explorer specific markup --> 
</xsl:if> 

Mozilla also provides JavaScript interfaces for XSLT, allowing a Web site to complete XSLT transformations in memory. You can do this using the global XSLTProcessor JavaScript object. XSLTProcessor requires you to load the XML and XSLT files, because it needs their DOM documents. The XSLT document, imported by the XSLTProcessor, allows you to manipulate XSLT parameters. XSLTProcessor can generate a standalone document using transformToDocument(), or it can create a document fragment using transformToFragment(), which you can easily append into another DOM document. Below is an example:

Mozilla提供了JavaScript接口,允许网站在内存中完成XSLT的转换。用户可以使用全局的JavaScript对象XSLTProcessorXSLTProcessor要求用户机咱XML和XSLT文件,因为它需要它们的DOM document。由XSLTProcessor加载(import)的XSLT document允许用户对XSLT参数进行操作。XSLTProcessor可以通过transformToDocument()生成独立的document,它也能通过 transformToFragment()生成document fragment,这让用户可以很方便地将其添加到别的DOM document。下面举个例子:

var xslStylesheet; 
var xsltProcessor = new XSLTProcessor(); 

// 加载xslt文件“example1.xsl”
var myXMLHTTPRequest = new XMLHttpRequest(); 
myXMLHTTPRequest.open("GET", "example1.xsl", false); 
myXMLHTTPRequest.send(null); 

// 获取XML cocument并加载它
xslStylesheet = myXMLHTTPRequest.responseXML; 

xsltProcessor.importStylesheet(xslStylesheet); 

// 加载xmlwenj“example1.xml”
myXMLHTTPRequest = new XMLHttpRequest(); 
myXMLHTTPRequest.open("GET", "example1.xml", false); 
myXMLHTTPRequest.send(null); 

var xmlSource = myXMLHTTPRequest.responseXML; 

var resultDocument = xsltProcessor.transformToDocument(xmlSource); 

After creating an XSLTProcessor, you load the XSLT file using XMLHttpRequest. The XMLHttpRequest's responseXML member contains the XML document of the XSLT file, which is passed to importStylesheet. You then use the XMLHttpRequest again to load the source XML document that must be transformed; that document is then passed to the transformToDocument method of XSLTProcessor. Table 8 features a list of XSLTProcessor methods.

创建XSLTProcessor之后,用户就可以用XMLHttpRequest()加载XSLT文件。XMLHttpRequest的成员变量responseXML的内容是对应这个XSLT文件的XML document,其中responseXML被传递给importStylesheet。之后用户再次使用XMLHttpRequest加载需要转换的XML文件,然后该文件被传递给XSLTProcessortransformToDocument函数。表8列出了XSLTProcessor的函数。

Table 8. XSLTProcessor methods
Method Description
void importStylesheet(Node styleSheet) Imports the XSLT stylesheet. The styleSheet argument is the root node of an XSLT stylesheet's DOM document.
DocumentFragment transformToFragment(Node source, Document owner) Transforms the Node source by applying the stylesheet imported using the importStylesheet method and generates a DocumentFragment. owner specifies what DOM document the DocumentFragment should belong to, making it appendable to that DOM document.
Document transformToDocument(Node source) Transforms the Node source by applying the stylesheet imported using the importStylesheet method and returns a standalone DOM document.
void setParameter(String namespaceURI, String localName, Variant value) Sets a parameter in the imported XSLT stylesheet.
Variant getParameter(String namespaceURI, String localName) Gets the value of a parameter in the imported XSLT stylesheet.
void removeParameter(String namespaceURI, String localName) Removes all set parameters from the imported XSLT stylesheet and makes them default to the XSLT-defined defaults.
void clearParameters() Removes all set parameters and sets them to defaults specified in the XSLT stylesheet.
void reset() Removes all parameters and stylesheets.

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