gem 'nkj'

require 'nkj'

# `jisx0213?` returns a boolean value whether or not the given all chars are included in JIS X 0213.
NKJ.jisx0213?('aあ!庵') #=> true
NKJ.jisx0213?('髙') #=> false

# `level1?` returns whether or not the given all chars are included Japanse Level1 Kanji.(第一水準)
NKJ.level1?('山') #=> true

# `level2?` returns whether or not the given all chars are included Japanse Level2 Kanji.(第二水準)
NKJ.level2?('丼') #=> true

# `level3?` returns whether or not the given all chars are included Japanse Level3 Kanji.(第三水準)
NKJ.level3?('﨑') #=> true

# `level4?` returns whether or not the given all chars are included Japanse Level4 Kanji.(第四水準)
NKJ.level4?('挻') #=> true