Why Scripts.Render invoke JsMinify.Process?

Question

I profiled my ASP.NET MVC application and I saw strange a function calls.

You can see it on image

Always when mvc render layout we invoke system.web.optimization.scripts.render which invoke JsMinify.Process and Minifier.MinifyJavaScript, but I thought what minification should be one time on the start app.

Am I right?

Maybe must I set some settings for optimization it?

Conditions:

• localhost
• release
• BundleTable.EnableOptimizations = true;

Answer 1

Great Question!

Intuitively, you are right, minification of assets should be performed on application Startup. You assume that assets are delivered identically to all browsers. But Microsoft believes that much of JS and CSS is browser specific.

If you check asp.net site's reference on ASP.NET 4.5 Bundling and Minification, they specifically state:

Bundling and minification in ASP.NET 4.5 is performed at runtime, so that the process can identify the user agent (for example IE, Mozilla, etc) , and thus, improve the compression by targeting the user browser (for instance, removing stuff that is Mozilla specific when the request comes from IE).

:

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What about caching?

Bundling isn't as obtuse as a profiled would have you think. If you look up MVC 4 Bundling and Minification reference, they point out:

Bundle Caching

Bundles set the HTTP Expires Header one year from when the bundle is created. If you navigate to a previously viewed page, Fiddler shows IE does not make a conditional request for the bundle, that is, there are no HTTP GET requests from IE for the bundles and no HTTP 304 responses from the server.

This is far more information than you need, but the message is that, JSMinify has a check for relevant cached minified assets.

When you factor in further that we already use minified version of our assets (eg jquery.min.js, jquery-ui.min.js), you can appreciate that .Net minification is a supplemental process.

Why does Minification of all types have to happen