【面试季二】前端性能优化_html/css_WEB-ITnose
这是一个老生常谈的内容了，90%的面试里都会问到，在这里只是再简单的整理一遍，以加强记忆巩固。
一 减少Http请求：主要可以通过合并图片、Css、Js和页面延迟加载等方法减少请求次数；
二 减少repaint和reflow:主要是指要尽量减少页面的重新渲染和重新布局，这个实际工作中基本是不可避免的，就合理使用即可；
三 减少对DOM的操作：主要是指尽量减少对DOM的增删改查这一类的节点操作，尽量使用局部变量，这个在某些项目中也是不可避免的，所以要合理应对；
四 使用JSON进行数据交换：JSON是一种轻量级的数据格式，也是JS自带的，所以有很多优点；
五 使用CDN加速：这个是最近多数公司都在使用的，中文是内容分发网络，可以就近分配内容，可以增加一些访问速度；
六 CSS和JS文件都尽量使用外链样式，并且将JS文件放在body最外边，我一般在写的时候都是放在html的最外边，基本一个意思。主要原因是因为JS具有阻塞特性会影响其他内容的加载和渲染。（我平时都说JS是单进程语言，暂时未仔细研究单进程和阻塞特性是否是一个东西。。。）
七 压缩JS文件：我一般都是用在线压缩工具，最近面试被问到有没有用过那种可以一边编写一边压缩的工具。。。?。。。如有知道的大牛，请告知一二；
八 压缩图片和合并图片：压缩图片我一般在切图的时候就会做了，在PS文件中存储切片时降低分辨率，选择适当的图片格式或是降低图片质量。不过自从retina屏出来以后我又开始纠结要不要这么做了，因为EXBoss用的是MacPro。。。这个各位大牛现在是怎么做的？用@2x.png这样来解决以外还有其他的吗？请指教！
以上总结来自这里，在这里借鉴一下，因为人家总结的比我好嘛~我只是简化后搬过来方便自己记忆，如有不明确或是不详细的地方，请查看原文。
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