[翻译]High Performance JavaScript(014)
Recursion Patterns 递归模式
When you run into a call stack size limit, your first step should be to identify any instances of recursion in the code. To that end, there are two recursive patterns to be aware of. The first is the straightforward recursive pattern represented in the factorial() function shown earlier, when a function calls itself. The general pattern is as follows:
当你陷入调用栈尺寸限制时,第一步应该定位在代码中的递归实例上。为此,有两个递归模式值得注意。首先是直接递归模式为代表的前面提到的factorial()函数,即一个函数调用自身。其一般模式如下:
function recurse(){
recurse();
}
recurse();
This pattern is typically easy to identify when errors occur. A second, subtler pattern involves two functions:
当发生错误时,这种模式比较容易定位。另外一种模式称为精巧模式,它包含两个函数:
function first(){
second();
}
function second(){
first();
}
first();
In this recursion pattern, two functions each call the other, such that an infinite loop is formed. This is the more troubling pattern and a far more difficult one to identify in large code bases.
在这种递归模式中,两个函数互相调用对方,形成一个无限循环。这是一个令人不安的模式,在大型代码库中定位错误很困难。
Most call stack errors are related to one of these two recursion patterns. A frequent cause of stack overflow is an incorrect terminal condition, so the first step after identifying the pattern is to validate the terminal condition. If the terminal condition is correct, then the algorithm contains too much recursion to safely be run in the browser and should be changed to use iteration, memoization, or both.
大多数调用栈错误与这两种模式之一有关。常见的栈溢出原因是一个不正确的终止条件,所以定位模式错误的第一步是验证终止条件。如果终止条件是正确的,那么算法包含了太多层递归,为了能够安全地在浏览器中运行,应当改用迭代,制
相关文档:
function db()
{
//活动编号
var activeid = Request.Form("activeid");
//用户名
var username = Request.Form("username");
//手机号码
var mobile = Request.Form("mobile");
var conn= Server.CreateObject("ADODB.connection");
var rs= Serve ......
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.
......
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 ......
Conditionals 条件表达式
Similar in nature to loops, conditionals determine how execution flows through JavaScript. The traditional argument of whether to use if-else statements or a switch statement applies to JavaScript just as it does to other languages. Since different b ......