June 2009
Intermediate to advanced
256 pages
7h 3m
English
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Chapter 6. Positioning Inline Scripts
The previous three chapters focused on the impact of external scripts. This chapter focuses on inline scripts (JavaScript included in the HTML document directly). Even though inline scripts don’t introduce additional HTTP requests, they can block resources in the page from being downloaded in parallel. They can also thwart progressive rendering. This chapter explains why the decisions of when and where to inline JavaScript have an impact on page performance.
Inline Scripts Block
Chapter 5 describes how external scripts block parallel downloads and
rendering. It’s not surprising that inline scripts have the same behavior
for the same reasons (preserving execution order and document.write dependencies). The Inline Scripts
Block example demonstrates this
behavior.
- Inline Scripts Block
http://stevesouders.com/cuzillion/?ex=10100&title=Inline+Scripts+Block
Figure 6-1 shows the HTTP requests issued for this page. In addition to the HTML document, there are two image requests, each configured to take one second. An inline script is inserted between these two images. The inline script is represented by a line in Figure 6-1. It does not generate an HTTP request, but the impact it has is observable.
Figure 6-1. Inline scripts block parallel downloads (six seconds)
The inline script is configured to take five seconds to execute. This is what causes the four seconds ...
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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.