Optimization
Ever since developers moved to more managed development languages, such as C# and .NET in general, the need for optimization has become less important. This is not to say that optimizing your code is not important--on the contrary, it still is, and it is important to understand as a SharePoint developer that items you implement and package to your solutions will affect the overall page payload for your users. As a developer, this might not seem such a big problem, but considering the fact that your page might get hundreds or thousands of active users, the lack of optimization soon starts to take its toll.
Optimizing the SharePoint Framework packages
When you start building solutions with SPFx, there's a nice way to view what kind of packages you are producing. As part of the toolchain, Microsoft has included Webpack Visualizer, which produces a nice overview of your overall bundle. This overview is accessible under /temp/stats, in a .html file:
This sample SPFx web part project...
