Technically, the iFrame itself is not responsive but that is what the library does: it wraps it in a container that has more responsive properties than the iFrame.

In addition, I think you may be overloading the word "responsive." This is not a post-message base iFrame resizer, it makes iFrames scale like images. This maintains an aspect ratio which is very desirable in many cases. Think a YouTube embed.

I guess the best way to think about it is that when you omit the height on an image, it will scale when you define its width. iFrames don't do that by default, but this allows them to be scaled.

Honestly I would be surprised to not see this keep growing. Most technology companies rely on Open Source and many are "giving back" as a way to help others how they were helped (or at the very least it's a great recruiting tool). The last start-up I worked at I worked on three different open source projects that we needed but could also help the community if they needed a similar solution.

We are a major player in Ember Fastboot. We're trying to open source more projects that have value, so it's nice to hear people notice!

I immediately thought this was a re-frame port to vanilla JavaScript

Thanks!

the post addresses this, and gives credit under the "Why?" section.

short version: it's meant to be smaller / avoid a jQuery dependency.

What exactly is "dangerous" about this? The functionality is pretty straightforward - it just creates a parent element of the correct width/height around an element that dictates the original elements height, and then resizes the inside one proportionately as needed for responsiveness (using CSS only).