Too many scripts will slow us down

I’ve been ‘away’ from this blog for a while. It’s been a very interesting year for me but I’ve been neglecting this blog for too long.

If you’ve read the previous posts, you can see I’m not a big fan of the Asp.Net postbacks and update panels. Too much information is sent back and forth for small actions that can be easily done in javascript.

As I’ve shown before, there are hugh performance benefits to using client side rendering in a web app. Instead of sending the entire HTML for every request, we load javascript code for creating that HTML once and after that we just send the data for subsequent requests.

One of the side effects of moving from server side rendering is that you start getting more and more javascript files. I’ve been using JQuery for a while, there are a lot of great plugins for JQuery, but loading all of those include files introduces some problems:

  1. More scripts = more requests = more loading time
  2. Managing includes can become messy

Using a Script Combiner to reduce the number of requests
Ideally you want to have only one js file and one css file, but you don’t want to have your files merged while you’re developing, a hugh file will be a pain to work with. The solution is to merge all the scripts into one big file later, either in the build process or at run time.
if you use the same scripts for all pages in your app (or if you have a one page app), merging during the build process is a good solution but I needed different files for different pages.

Asp.Net AJAX 3.5
If you’re using Asp.Net AJAX 3.5, achieving this is very simple. The scripts from Microsoft will already be combined by default and to add your own scripts all you need to do is include your scripts using the ScriptManager.

<asp:ScriptManager runat="server" ID="ScriptManager1" >
            <asp:ScriptReference Path="~/JScript1.js" />
            <asp:ScriptReference Path="~/JScript2.js" />

Script Combiner - The Other Solution
If you don’t use Asp.Net AJAX and don’t want those scripts loaded (or you’re still using 2.0) you can create your own handler to combine scripts.
Here’s a project I foundby Omar Al Zabir (Who wrote the excellent book Building a Web 2.0 Portal with ASP.NET 3.5 and co-founded PageFlakes)
You might want to change the way you decide which scripts to load, I use an xml configuration file to specify the location of each script file and which js files should be loaded based on the page name that’s passed to the handler. (I use the page name as the key for now). I also have a separate path for the minified version and the debug version, and based on a config I use the right one

   <Script name=”jquery” minPath=”Scripts/JQuery/jquery.1.2.6.min.js” debugPath=”Scripts/JQuery/jquery.1.2.6.js”/>
   <Script name=”jqvalidation” minPath=”Scripts/JQuery/plugins/jquery.validate.min.js” debugPath=”Scripts/JQuery/plugins/jquery.validate.js”/>
   <Page name=”home” Scripts=”jquery,jqvalidation” />

There are several benefits when using this custom handler

  • You can use it for css files too
  • It compresses the js files using gzip
  • The files are only read from the file system once and are then cached on the server for subsequent requests
  • You can easily add versioning to the handler and set client side caching to never expire.