[翻译]High Performance JavaScript(011)
Repaints and Reflows 重绘和重排版
Once the browser has downloaded all the components of a page—HTML markup, JavaScript, CSS, images—it parses through the files and creates two internal data structures:
当浏览器下载完所有页面HTML标记，JavaScript，CSS，图片之后，它解析文件并创建两个内部数据结构：
A DOM tree
A representation of the page structure
一棵DOM树
表示页面结构
A render tree
A representation of how the DOM nodes will be displayed
一棵渲染树
表示DOM节点如何显示
The render tree has at least one node for every node of the DOM tree that needs to be displayed (hidden DOM elements don't have a corresponding node in the render tree). Nodes in the render tree are called frames or boxes in accordance with the CSS model that treats page elements as boxes with padding, margins, borders, and position. Once the DOM and the render trees are constructed, the browser can display ("paint") the elements on the page.
渲染树中为每个需要显示的DOM树节点存放至少一个节点（隐藏DOM元素在渲染树中没有对应节点）。渲染树上的节点称为“框”或者“盒”，符合CSS模型的定义，将页面元素看作一个具有填充、边距、边框和位置的盒。一旦DOM树和渲染树构造完毕，浏览器就可以显示（绘制）页面上的元素了。
When a DOM change affects the geometry of an element (width and height)—such as a change in the thickness of the border or adding more text to a paragraph, resulting in an additional line—the browser needs to recalculate the geometry of the element as well as the geometry and position of other elements that could have been affected by the change. The browser invalidates the part of the render tree that was affected by the change and reconstructs the render tree. This process is known as a reflow. Once the reflow is complete, the browser redraws the affected parts of the screen in a
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function
parseXML
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xmlUrl
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{
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xmlDoc
......
Closure中文翻译为闭包.字面上来理解就是"封闭的包".(这是一句废话)
闭包是什么?
书面解释为:
所谓“闭包”，指的是一个拥有许多变量和绑定了这些变量的环境的表达式（通常是一个函数），因而这些变量也是该表达式的一部分。
我认为闭包就是能够读/写函数内部的某些变量的子函数,并将这些变量保存 ......
typeof 是JavaScript的运算符
——返回一个用来表示表达式的数据类型的字符串
typeof[(] expression [)] //typeof语法中的圆括号是可选项
typeof 运算符@import url(../html-vss/msdnie4a.css);
typeof
运算符把类型信息当作字符串返回。typeof
返回值有� ......
隐藏成员变量
在函数体内定义的变量为局部变量，离开函数就挂掉了
在函数体内使用this.成员变量名，则为window对象级变量，即全局变量
故需要这样隐藏成员变量，向外只暴露get、set函数
function testClass(name){
var _firstname=name;
return {
getname : function() {
return _fir ......
使用javascript创建Microsoft XML DOM,就可以完成这一工作.
// 装入数据.
var source = new ActiveXObject("Microsoft.XMLDOM");
source.async = false
source.load("history.xml");
// 装入样式表.
var stylesheet = new ActiveXObject("Microsoft.XMLDOM");
stylesheet.async = false
stylesheet.load( ......
