[翻译]High Performance JavaScript(019)
第六章 Responsive Interfaces 响应接口
There's nothing more frustrating than clicking something on a web page and having nothing happen. This problem goes back to the origin of transactional web applications and resulted in the now-ubiquitous "please click only once" message that accompanies most form submissions. A user's natural inclination is to repeat any action that doesn't result in an obvious change, and so ensuring responsiveness in web applications is an important performance concern.
没有什么比点击页面上的东西却什么也没发生更令人感到挫折了。这个问题又回到了原始网页交互程序和现在已无处不在的提交表单时弹出的“请勿重复提交”消息上面。用户自然倾向于重复尝试这些不发生明显变化的动作，所以确保网页应用程序的响应速度也是一个重要的性能关注点。
Chapter 1 introduced the browser UI thread concept. As a recap, most browsers have a single process that is shared between JavaScript execution and user interface updates. Only one of these operations can be performed at a time, meaning that the user interface cannot respond to input while JavaScript code is executed and vice versa. The user interface effectively becomes "locked" when JavaScript is executing; managing how long your JavaScript takes to execute is important to the perceived performance of a web application.
第一节介绍了浏览器UI线程概念。总的来说，大多数浏览器有一个单独的处理进程，它由两个任务所共享：JavaScript任务和用户界面更新任务。每个时刻只有其中的一个操作得以执行，也就是说当JavaScript代码运行时用户界面不能对输入产生反应，反之亦然。或者说，当JavaScript运行时，用户界面就被“锁定”了。管理好JavaScript运行时间对网页应用的性能很重要。
The Browser UI Thread 浏览器UI线程
The process shared by JavaScript and user interface updates is frequently referred to as the browser UI thread (though the term "thread" is not necessarily accurate for all browsers). The UI thread works on a sim
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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 ......
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(){
......
第五章 Strings and Regular Expressions 字符串和正则表达式
Practically all JavaScript programs are intimately tied to strings. For example, many applications use Ajax to fetch strings from a server, convert those strings into more easily usable JavaScript objects, and ......
A Note on Benchmarking 测试基准说明
Because a regex's performance can be wildly different depending on the text it's applied to, there's no straightforward way to benchmark regexes against each other. For the best result, you need to benchmark your regexes on test strings o ......
String Trimming 字符串修剪
Removing leading and trailing whitespace from a string is a simple but common task. Although ECMAScript 5 adds a native string trim method (and you should therefore start to see this method in upcoming browsers), JavaScript has not historically in ......
