alt Hacker NewsHTML is a markup language, not a programming language. It's like asking why Markdown can't handle includes. Some Markdown editors support them (just like some server-side tools do for HTML), but not all.
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This isn’t programming. It’s transclusion[0]. Essentially, iframes and images are already forms of transclusion, so why not transclude html and have the iframe expand to fit the content?
As I wrote that, I realized there could be cumulative layout shift, so that’s an argument against. To avoid that, the browser would have to download all transcluded content before rendering. In the past, this would have been a dealbreaker, but maybe it’s more feasible now with http multiplexing.
[0] https://en.m.wikipedia.org/wiki/Transclusion#Client-side_HTM...
Well, asciidoc - a markup language supports includes, so the "markup languages" analogy doesn't hold.
https://docs.asciidoctor.org/asciidoc/latest/directives/incl...
That’s the Hyper part of HTML, and what makes it special.
It’s made to pull in external resources (as opposed to other document formats like PDF).
Scripts, stylesheets, images, objects, favicons, etc. HTML is thematically similar.
I think this is the most likely answer.
I'm not defending it, because when I started web development this was one of the first problems I ran into as well -- how the heck do you include a common header.
But the original concept of HTML was standalone documents, not websites with reusable components like headers and footers and navbars.
That being said, I still don't understand why then the frames monstrosity was invented, rather than a basic include. To save on bandwidth or something?
Markdown doesn't have this common HTML pattern of wanting to include a header/footer in all pages of a site.
Including another document is much closer to a markup operation than a programming operation. We already include styles, scripts, images, videos, fonts...why not document fragments?
Markdown can't do most of those, so it makes more sense why it doesn't have includes, but I'd still argue it definitely should. I generally dislike LaTeX, but about the only thing I liked about it when writing my thesis was that I could have each chapter in its own file and just include all of them in the main file.