[翻译]High Performance JavaScript(024)
Data Format Conclusions 数据格式总结
Favor lightweight formats in general; the best are JSON and a character-delimited custom format. If the data set is large and parse time becomes an issue, use one of these two techniques:
总的来说越轻量级的格式越好，最好是JSON和字符分隔的自定义格式。如果数据集很大或者解析时间成问题，那么就使用这两种格式之一：
• JSON-P data, fetched using dynamic script tag insertion. This treats the data as executable JavaScript, not a string, and allows for extremely fast parsing. This can be used across domains, but shouldn't be used with sensitive data.
JSON-P数据，用动态脚本标签插入法获取。它将数据视为可运行的JavaScript而不是字符串，解析速度极快。它能够跨域使用，但不应涉及敏感数据。
• A character-delimited custom format, fetched using either XHR or dynamic script tag insertion and parsed using split(). This technique parses extremely large datasets slightly faster than the JSON-P technique, and generally has a smaller file size.
字符分隔的自定义格式，使用XHR或动态脚本标签插入技术提取，使用split()解析。此技术在解析非常大数据集时比JSON-P技术略快，而且通常文件尺寸更小。
The following table and Figure 7-1 show all of the performance numbers again (in order from slowest to fastest), so that you can compare each of the formats in one place. HTML is excluded, since it isn't directly comparable to the other formats.
下表和图7-1再次显示了所有方法的性能数据（按照从慢到快的顺序），你可以在此比较每种格式的优劣。HTML未包括，因为它与其他格式不能直接比较。
Figure 7-1. A comparison of data format download and parse times
图7-1 各种数据格式下载和解析的时间
Keep in mind that these numbers are from a single test run in a single browser. The results should be used as general indicators of performance, not as hard numbers. You can run these tests yourself at http://techfoolery.com/formats/.
请注意，这些�
相关文档：
＜script language="javaScript"＞
function closeWindow()
{
window.opener = null;
window.open(' ', '_self', ' ');
window.close();
}
＜/script＞
＜input type='button' value='关闭窗口' onClick="closeWindow()"＞
或
＜input type="button" value="� ......
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� ......
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．
......
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，JavaScri ......
