Re: FAQ Topic - What online resources are available? (2009-01-29)

Jorge wrote:
On Jan 29, 1:00 am, "FAQ server" <javascr...@xxxxxxxxxxxxxx> wrote:
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FAQ Topic - What online resources are available?
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PLUS:

Crockford's videos at <http://developer.yahoo.com/yui/theater/> :




Ajax Performance:

<http://video.yahoo.com/watch/4141759/11157560>


| Its a very dry topic. Its a very heavy topic. So we'll sort of ease
| into it.

This seems disappointing. I want the gory details and it looks like this video is not going to provide them.

The Ajax performance video mentions that IE 8 spends more time on layout and rendering.

The stats were taken from top 100 Alexa pages. These pages aren't rich applications. Many are poorly authored HTML with table-based layouts. For example, the source code of http://www.yahoo.com/ is of very poor quality.

Back to the video: If layout and rendering takes a bulk of the time, how can we test that?

On YSlow:
| ah so one thing we need to optimize is the startup. Getting the
| initial page load in and, you know, the work we've done here on
| exceptional performance is absolutely the right stuff to be looking at
| in order to reduce the latency of the (uh) page startup.

Latency is often used to mean network latency -- how much time it takes for the client to get its first byte of an HTTP response from the server. He is seems to be using "latency" to describe time from request to when the page is ready to use.

According to the statistics mentioned in the lecture, layout and rendering are where the browser spends most of its time. Thus, it would be a good idea to talk about how to effectively tune these, showing an example starting from taking statistics, to assessing the problem, to coming up with a solution.

The video does not describe how to identify and solve these problems.

"Make good use of Ajax Libraries"
| I recommend you make good use of Ajax libraries. Particularly YUI, I'm
| a big fan of that. Effective code reuse will make your widgets more
| effective.

I can't agree that the first sentence is good advice. The second sentence is too vague. It should absolutely not be considered an implication of the first.

The general purpose libraries usually contain a lot of code that is not executed for a given application. An application using a general-purpose library might likely use only a small portion of that library. That is not "good use" of a library. It might be considered to be "effective" in the sense that it would fulfill a requirement. However, it would not be efficient. The library, in that case would increases the time to onload.

A library which adds an onunload handler will prevend fastfb (discussed here recently). All of the major libraries do that.

The largest performance benefits to be gained will be through the design and architecture of the application. The code must be tunable before it can be tuned. The messier the code, the harder it is to tune.

Building, minifying, and load order are important factors in actual performance and perceived performance.

The part: "your intuition is usually wrong." would be a great recommendation for managers to watch. Loop that, and you'll have an effective video for managers.

Conclusion: I do not find this video to be effective learning material for developing high-performance, Ajax applications.

Garrett

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