[翻译]High Performance JavaScript(026)
Use the Fast Parts 使用速度快的部分
Even though JavaScript is often blamed for being slow, there are parts of the language that are incredibly fast. This should come as no surprise, since JavaScript engines are built in lower-level languages and are therefore compiled. Though it's easy to blame the engine when JavaScript appears slow, the engine is typically the fastest part of the process; it's your code that is actually running slowly. There are parts of the engine that are much faster than others because they allow you to bypass the slow parts.
虽然JavaScript经常被指责缓慢，然而此语言的某些部分具有难以置信的快速。这不足为奇因为JavaScript引擎由低级语言构建。虽然JavaScript速度慢很容易被归咎于引擎，然而引擎通常是处理过程中最快的部分，实际上速度慢的是你的代码。引擎的某些部分比其它部分快很多，因为它们允许你绕过速度慢的部分。
Bitwise Operators 位操作运算符
Bitwise operators are one of the most frequently misunderstood aspects of JavaScript. General opinion is that developers don't understand how to use these operators and frequently mistake them for their Boolean equivalents. As a result, bitwise operators are used infrequently in JavaScript development, despite their advantages.
位操作运算符是JavaScript中经常被误解的内容之一。一般的看法是，开发者不知道如何使用这些操作符，经常在布尔表达式中误用。结果导致JavaScript开发中不常用位操作运算符，尽管它们具有优势。
JavaScript numbers are all stored in IEEE-754 64-bit format. For bitwise operations, though, the number is converted into a signed 32-bit representation. Each operator then works directly on this 32-bit representation to achieve a result. Despite the conversion, this process is incredibly fast when compared to other mathematical and Boolean operations in JavaScript.
JavaScript中的数字按照IEEE-754标准64位格式存储。在位运算中，数字被转换为有符号32位格式。每种操作均直接操作在这个32位数上�
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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� ......
玩PHP、Delphi、Java基本上都有对象，习惯这种思路后上手任何语言都想靠OO思路，这绝不是在赶时髦，而是把相关代码进行内聚的确可以体会到维护的方便！
在JavaScript中如何创建对象？
JavaScript是基于对象的！它也是以Object为根类，其它类继承之。在根类提供了几个方法。供继承类使用！
以下是创建对象的例子：
funct ......
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;
......
function total(){
var i=0;
for(j=1;j<=20;j++)
{
var step="step"+j;
if(document.getElementById(step)){
if(document.getElementById(step).checked==true)
{
i=i+parseInt(document.getElementById(step).value);
}
}
}
document.getElementById("total").innerHTML = i;
}
function Resetvalue(){
......
第四章 Algorithms and Flow Control 算法和流程控制
The overall structure of your code is one of the main determinants as to how fast it will execute. Having a very small amount of code doesn't necessarily mean that it will run quickly, and having a large amount of code ......
