前端性能优化-gzip

为什么要开启GZIP

我们需要下载一个100KB的Javascript文件，正常的下载量就是100KB，如果我们把文件在服务端压缩一下，压缩成30kb，下载到客户端再进行解压，这样就减少了大量的HTTP的传输时间，这就是GZIP的作用。

如何开启服务器的GZIP

我们以windows版的Apache2.4为例，打开httpd.conf文件，因为开启GZIP需要mod_deflate.so，所以首先把解注mod_deflate.so，然后增加下面的配置项：

#开启GZIP

<IfModule mod_deflate.c>
   SetOutputFilter DEFLATE
   # example of how to compress ONLY html, plain text and xml
   # AddOutputFilterByType DEFLATE text/plain text/html text/xml
   # Don't compress binaries
   SetEnvIfNoCase Request_URI .(?:exe|t?gz|zip|iso|tar|bz2|sit|rar) no-gzip dont-vary
   # Don't compress images
   SetEnvIfNoCase Request_URI .(?:gif|jpe?g|jpg|ico|png)  no-gzip dont-vary
   # Don't compress PDFs
   SetEnvIfNoCase Request_URI .pdf no-gzip dont-vary
   # Don't compress flash files (only relevant if you host your own videos)
   SetEnvIfNoCase Request_URI .flv no-gzip dont-vary
   # Netscape 4.X has some problems
   BrowserMatch ^Mozilla/4 gzip-only-text/html
   # Netscape 4.06-4.08 have some more problems
   BrowserMatch ^Mozilla/4.0[678] no-gzip
   # MSIE masquerades as Netscape, but it is fine
   BrowserMatch MSIE !no-gzip !gzip-only-text/html
   # Make sure proxies don't deliver the wrong content
   Header append Vary User-Agent env=!dont-vary
   # Setup custom deflate log
   DeflateFilterNote Input instr
   DeflateFilterNote Output outstr
   DeflateFilterNote Ratio ratio
   LogFormat '"%r" %{outstr}n/%{instr}n %{ratio}n%%' DEFLATE
   CustomLog logs/deflate_log DEFLATE
</IfModule>

重启Apache，配置生效！

对比测试

我们以jquery-1.7.1.js为例，在不开启GZIP和开启GZIP下的文件大小进行对比

1.开启GZIP，文件传输大小为32.7KB

2.未开启GZIP，文件的传输大小为92.0KB，即文件的实际大小