[翻译]High Performance JavaScript(002)

Grouping Scripts 成组脚本
    Since each <script> tag blocks the page from rendering during initial download, it's helpful to limit the total number of <script> tags contained in the page. This applies to both inline scripts as well as those in external files. Every time a <script> tag is encountered during the parsing of an HTML page, there is going to be a delay while the code is executed; minimizing these delays improves the overall performance of the page.
    由于每个<script>标签下载时阻塞页面解析过程，所以限制页面的<script>总数也可以改善性能。这个规则对内联脚本和外部脚本同样适用。每当页面解析碰到一个<script>标签时，紧接着有一段时间用于代码执行。最小化这些延迟时间可以改善页面的整体性能。
    The problem is slightly different when dealing with external JavaScript files. Each HTTP request brings with it additional performance overhead, so downloading one single 100 KB file will be faster than downloading four 25 KB files. To that end, it's helpful to limit the number of external script files that your page references. Typically, a large website or web application will have several required JavaScript files. You can minimize the performance impact by concatenating these files together into a single file and then calling that single file with a single <script> tag. The concatenation can happen offline using a build tool (discussed in Chapter 9) or in real-time using a tool such as the Yahoo! combo handler.
    这个问题与外部JavaScript文件处理过程略有不同。每个HTTP请求都会产生额外的性能负担，下载一个100KB的文件比下载四个25KB的文件要快。总之，减少引用外部脚本文件的数量。典型的，一个大型网站或网页应用需要多次请求JavaScript文件。你可以将这些文件整合成一个文件，只需要一个<script>标签引用，就可以减少性能损失。这一系列的工作可通过一个打包工具实现（我们在第9章讨论），或者一个实时工具，诸如“Yahoo! combo handler”。
    Yahoo! created the