Eugene's Blog

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Serve files with nginx conditionally

Time and again working on big web applications we customize files based on user’s platform, and their preferences. We can send different files to legacy browsers, different CSS and JS to mobile browsers depending on their form factor, different images to accomodate bandwidth requirements, and so on.

This post was prompted by my desire to serve sprites produced by grunt-tight-sprite as WebP images to WebP-capable browsers falling back to “classic” image formats for the rest using nginx. While it is hardly a new topic, I was not satisfied with existing solutions, which all used if and rewrite, instead of simpler methods.

Obviously the core solution can be used to serve almost any file conditionally, not only images, but all examples will be about WebP.

CG: code generation in JavaScript

ClubAjax invited me to speak about technologies behind Heya, specifically about code generative solutions behind heya-pipe. Pipes are built on a firm foundation of functional programming (FP), and it allows us to use a wide range of technologies to optimize their performance including generating code on the fly (code generation AKA CG).

As soon as we are talking about CG, the first question to ask is: “How to debug such code?”. Heya provides answers for that too. But no spoilers.

Direct link: Practical pairing of generative programming with functional programming.

Switched to Octopress

After 8 years I decided to switch to Octopress. Being a server-less framework, it allows my web site to scale better, and, the most important thing for me, reduces expences on administring an active server (less active components to update). An additional bonus is that it reduces requirements for a web site host, which allows me to be more flexible when selecting a hosting company.

All old links are supposed to work as they used to be redirecting to new URLs. Please let me know, if something doesn’t work for you.

Slides: optimization of modern web applications

I spoke at ClubAjax about optimization of modern web applications. Usually I speak about theoretical matters, but this time I decided to go practical. This is a huge topic and it was blogged/debated/presented to death, including my Improving performance…. Yet I decided to add to it after realizing that many things have changed in last years, including how we build web applications. I concentrated on technical aspects completely bypassing all other areas (e.g., a psychological angle).

Fair warning: these slides were my talking points. Feel free to ask me, if you found some slides lacking or even puzzling, or can improve on mentioned techniques.

Direct link: Optimization of modern web applications.

More on 0ms timeouts

Once I wrote a blog post On JavaScript, EDP, and 0ms timeouts, which discussed a "smart" trend to pepper code with timeouts of … 0ms: setTimeout(f, 0). Authors of those "programming pearls" genuinely believed that this code reschedules a function call to the next available time slice after the code that set the timer was executed without introduction of a delay (after all it is 0ms!). In reality a typical delay was 10-20ms. With new generation of browsers it starts with 4ms and jumps to 1000ms for non-current/hidden tabs.

OOP in JS slides

Finally: my open source JavaScript project DCL is built on ideas described in this article. Available for node.js and modern browsers, it implements OOP with mixins and AOP at "class" and object level. Read documentation and background articles on, clone its code on, and follow @dcl_js.

Once again I was invited in ClubAjax to speak about JavaScript. This time I did a presentation based in part on my previous blog post OOP and JS. Slides and talk revisit OOP, mixins, AOP, chaining, and other related techniques I discussed in my blog. Of course, OOP deficiencies were discussed at length too. I suggest to look at slides and read the blog post – it will give you a better picture.

I feel that such basic programming techniques are essential for everyday work. Done right they provide a solid foundation for our projects. That’s why I intend to build the next generation of OOP, AOP, FP libraries building on existing proven technologies.

Direct link: OOP in JS.

OOP and JS

Finally: my open source JavaScript project DCL is built on ideas described in this article. Available for node.js and modern browsers, it implements OOP with mixins and AOP at "class" and object level. Read documentation and background articles on, clone its code on, and follow @dcl_js.

Almost any Java programmer, who starts to study JS groking its OOP facilities and a dynamic nature of JS, thinks that they can be greatly improved and starts its own OOP library/helpers. Majority of them left forgotten when their authors learn more and more details and patterns of JS, yet some grow to fruition and being marketed. This article is dedicated to such people.

The goal of this article is to go over common OOP techniques suitable for JS, their pitfalls, problems, and trade-offs.

Using Dojo Rich Editor with Django’s Admin

Many years ago I decided to replace plain text areas in Django’s Admin with rich text editor, so I can edit HTML on my blog using WYSIWYG. Six (yes, 6) years ago I looked around and selected TinyMCE. Over time it turned out that I was forced to upgrade TinyMCE and the link script I had because new browsers continue breaking my rich editor editing. Finally it stopped working again in all modern browsers, and I decided that enough is enough. It is time to replace it. This time I settled on Dojo’s Rich Editor hosted on Google CDN — simple, functional, less work to set up.

Exciting JavaScript Part II

This month I continued my presentation at ClubAJAX. Last time I did a survey of what is available in JavaScript, and concentrated on object-oriented (OOP) and aspect-oriented (AOP) techniques. This time I continued the survey, and talked about functional programming (FP), and domain-specific languages (DSL). And as promised I touched the code generation facilities too.

I suggest to read the first part before.


Direct link: Exciting JavaScript – Part II.