Sure, but only for implementing your own. In practice they don't typically require the author of the page to know any Javascript. I'm using a client-side include by writing only HTML tags (with a 'remote-src' attribute).
It's no different from not having to know C++ in order to write HTML which is rendered by C++ code. The implementation just doesn't matter, because the user (in this case the page/site author) never needs to examine it.
Sure, but only for implementing your own. In practice they don't typically require the author of the page to know any Javascript. I'm using a client-side include by writing only HTML tags (with a 'remote-src' attribute).
It's no different from not having to know C++ in order to write HTML which is rendered by C++ code. The implementation just doesn't matter, because the user (in this case the page/site author) never needs to examine it.