A look into the Network Information API. Incrediblely useful for those dealing with performance issues on low level devices but still want to show their website at its peak for requests coming from desktops.
Imagine you're visiting YouTube on your smartphone or tablet. You're at home and connected over Wi-Fi. In such cases, you don't care about the number of bytes that are being downloaded, you're only interested in high quality video content. This isn't true if you're connected over a slow mobile connection. In that case, you want to see the video, the quality is secondary. I should be clear that every developer who wants a website to be really good still has to optimize the assets it serves to allow pages to load as fast as possible. However, in the above example, serving up a high resolution video isn't a waste of the user's bandwidth, but an improvement of the user experience. The Network Information API is exactly what we need to find out more about the network connection of the device.