tiny-segmenter
Super compact Japanese tokenizer in Javascript. http://chasen.org/~taku/software/TinySegmenter/
kuroshiro
kuroshiro is a Japanese language library for converting Japanese sentence to Hiragana, Katakana or Romaji with furigana and okurigana modes supported.
react-composition-input
An input component optimized for languages which need composition such as Chinese, Japanese etc.