I chose to use the 'elements' collection rather than choosing which elements to include (ie this supports inputs, textareas, buttons and anything else I didn't think of). It could be a bit simpler if we assume the element is a form. Even simpler if it's a fieldset (that has a disabled property). But I didn't want to limit it too much.
Unfortunately JS is quite ugly compared to Ruby. And 'prettier' made it uglier in my opinion.
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