I see various #JavaScript and #Dart libraries offering functions for detecting #Japanese kanji characters, but they almost always do this in a limited way that misses a huge number of characters, i.e. nothing beyond the #Unicode BMP, or even missing ranges in the BMP.
The only way to do this right is to
1. Work with codepoints, not UTF-16 code units
2. Look at the Unicode script property, which should be `Han` for kanji/hanzi












