Chapter 5. The Frontend

CHAPTER 4 EXPLORES HOW TO MIGRATE THE RESPONSIVENESS PARADIGM FROM THE CLIENT SIDE TO THE BACKEND. The concept is two-fold: first, load device-appropriate content and serve a dedicated experience from the backend; second, avoid the anti-pattern of loading the content for all devices. This lowers the overall payload of the page, and reduces what the client device has to do to finally render a page.

But what if your infrastructure, business model, or team’s skill set aren’t conducive to a server-side solution? In this case, there are ways to achieve similar performance gains from purely client-side solutions.

In this chapter, we direct our focus back to the frontend and discuss other ways to facilitate the same patterns.

Working with Images

As Steve Souders shows us via his Interesting Stats page in the HTTP Archive, the biggest contributor to page payload are the images on a page (see Figure 5-1). Thus, arguably the biggest impact we can have on responsive performance from the client side is to optimize the delivery of images to mobile clients.

Responsive images in the past have been looked at as needing to scale with a page as the viewport shrinks. Chapter 1 presents a competitive analysis that illustrates how this has usually been achieved by either just resizing images via CSS, or saving images twice as large as necessary and then scaling them down via CSS. But again, these solutions are actually performance anti-patterns: loading the same assets for all devices, ...

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