Kanji are often made of up other kanji stuck together. In most electric dictionaries you can search by radicals, but not all kanji are radicals; radicals are typically only minimal, indivisible units. This means that even if you recognize the left and right halves of kanji, for example, you may not be able to search them in a conventional dictionary. Examples of characters where this could be an issue are 蹄, 榎, 鮗.
Kanji Club works around this using kanji composition data, so kanji can be made up of arbitrary other kanji rather than just radicals. As a technical note, the preprocessed data is still only around 2MB, so all the search is in the browser - the whole site is static.
https://commons.wikimedia.org/wiki/Commons:Chinese_character...
I've already found it pretty useful as is, though there's still much left to do. Would love to have any comments on it.