[翻译]High Performance JavaScript(028)
JavaScript Minification JavaScript紧凑
JavaScript minification is the process by which a JavaScript file is stripped of everything that does not contribute to its execution. This includes comments and unnecessary whitespace. The process typically reduces the file size by half, resulting in faster downloads, and encourages programmers to write better, more extensive inline documentation.
JavaScript紧凑指的是剔除一个JavaScript文件中一切运行无关内容的过程。包括注释和不必要的空格。该处理通常可将文件尺寸缩减到一半，其结果是下载速度更快，并鼓励程序员写出更好，更详细的内联文档。
JSMin (http://www.crockford.com/javascript/jsmin.html), developed by Douglas Crockford, remained the standard in JavaScript minification for a long time. However, as web applications kept growing in size and complexity, many felt it was time to push JavaScript minification a step further. This is the main reason behind the development of the YUI Compressor (http://developer.yahoo.com/yui/compressor/), a tool that performs all kinds of smart operations in order to offer a higher level of compaction than other tools in a completely safe way. In addition to stripping comments and unnecessary whitespace, the YUI Compressor offers the following features:
JSMin（http://www.crockford.com/javascript/jsmin.html），由Douglas Crockford开发，它保持了JavaScript紧凑标准很长一段时间。然而随着网络应用程序在规模和复杂性上不断增长，许多人认为JavaScript紧凑应当再向前推进一步。这是开发YUI压缩器的主要原因（http://developer.yahoo.com/yui/compressor/）它提供了所有类型的智能操作，为了提供比其它工具更高级的紧凑操作并且以完全安全的方法实现。除了剔除注释和不必要的空格，YUI压缩器还提供以下功能：
• Replacement of local variable names with shorter (one-, two-, or three-character) variable names, picked to optimize gzip compression downstream
将局部变量名替换以更短的形式（1个，2个，或3个字符），以优化后续的gzip压缩工作
• Rep
相关文档：
本文主要是出于有朋友使用我原来写的autocomplete的JS控件。当数据量大的时候，会出现效率极其慢的情况，我在这段时间做出的一些测试也及一些经验，与大家分享，如果有错的地方，还请指出。
经过测试，我们会发现如下的情况或者说的结论，如果您的测试结果与我的不符，请说明原因，以便相互学习。
1）当一个较大的HTML字� ......
常规的方法是将年月日取出，然后分别判断范围，然后就判断闰年2月的天数
可以通过new Date(string)的构造，比较年月日字符是否发生变化判断。
function CheckDate(text) {
if (!text) return false;
text = text.replace(/[\/-]0?/g, "/");
if (!text.match(/^\d{4}\/\d{1,2}\/\d{1,2}$/)) return true;
......
AJAX (异步 JavaScript 和 XML) 是个新产生的术语,专为描述JavaScript的两项强大性能.这两项性
能在多年来一直被网络开发者所忽略,直到最近Gmail, Google suggest和google Maps的横空出世才使人
们开始意识到其重要性.
这两项被忽视的性能是:
* 无需重新装载整个页面便能向服务器发送请求.
* 对XML文档的解析和处理．
......
Yielding with Timers 用定时器让出时间片
Despite your best efforts, there will be times when a JavaScript task cannot be completed in 100 milliseconds or less because of its complexity. In these cases, it's ideal to yield control of the UI thread so that UI updates may occur ......
Splitting Up Tasks 分解任务
What we typically think of as one task can often be broken down into a series of subtasks. If a single function is taking too long to execute, check to see whether it can be broken down into a series of smaller functions that complete in smaller ......
