September 2007
Intermediate to advanced
170 pages
4h 24m
English
Content preview from High Performance Web Sites
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Worst Case: Scripts at the Top
At this point, the effects that scripts can have on web pages are clear:
Content below the script is blocked from rendering.
Components below the script are blocked from being downloaded.
If scripts are put at the top of the page, as they usually are, everything in the page is below the script, and the entire page is blocked from rendering and downloading until the script is loaded. Try out the following example.
- Scripts at the Top
Because this entire page is blocked from rendering, it results in the blank white screen phenomenon described in Chapter 7. Progressive rendering is critical for a good user experience, but slow scripts delay the feedback users crave. Also, the reduction of parallelized downloads delays how quickly images are displayed in the page. Figure 8-5 shows how the components in the page are downloaded later than desired.
Figure 8-5. Script at the top blocks the entire page
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.