Analyzing performance

Dealing with performance issues is initially a problem of intelligence gathering. There can be multiple reasons why an application feels slow, and the feedback of users often doesn't help. Describing a part of the app as "sticky" just isn't a great way to diagnose the root cause. We need to get firm facts and figures in front of us before we can hope to find a solution. While we'll look at metrics such as rendering and response times, there are many considerations that must be taken into account, such as memory usage and user perception. These topics are left as an exercise for the reader.

The Chrome Developer Tools come to the rescue again. This time, we'll look at two main features that help diagnose performance problems: profiles and the timeline.

Note

In general, there are two situations in which Ext JS applications feel slow: poor design decisions and over-complicated apps. Having said that, these techniques are invaluable when the problem...