Imager.js
Responsive images while we wait for srcset to finish cooking
...We wanted something simple, which works and which is fast as well as network friendly (only download what you need, when you need it). Imager has the ability to replace {width} with a non-numeric value if you provide the widthInterpolator option, which is a function that returns the string to be injected into the image URL for a given width. This feature allows you to use a human-readable name or integrate with third-party image providers.