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rubyregexunicodeemoji

How do I remove emoji from string

My problem is to remove emoji from a string, but not CJK (Chinese, Japanese, Korean) characters from a string using regex. I tried to use this regex:

REGEX = /[^\u1F600-\u1F6FF\s]/i

This regex works fine except it also detects the Chinese, Japanese and Korean character where I need those characters. Any idea how to solve this issue?

Solution

  • Karol S already provided a solution, but the reason might not be clear:

    "\u1F600" is actually "\u1F60" followed by "0":

    "\u1F60"    # => "ὠ"
"\u1F600"   # => "ὠ0"

    You have to use curly braces for code points above FFFF:

    "\u{1F600}" #=> "😀"

    Therefore the character class [\u1F600-\u1F6FF] is interpreted as [\u1F60 0-\u1F6F F], i.e. it matches "\u1F60", the range "0".."\u1F6F" and "F".

    Using curly braces solves the issue:

    /[\u{1F600}-\u{1F6FF}]/

    This matches (emoji) characters in these unicode blocks:

    You can also use unpack, pack, and between? to achieve a similar result. This also works for Ruby 1.8.7 which doesn't support Unicode in regular expressions. 

    s = 'Hi!😀'
#=> "Hi!\360\237\230\200"

s.unpack('U*').reject{ |e| e.between?(0x1F600, 0x1F6FF) }.pack('U*')
#=> "Hi!"

    Regarding your Rubular example – Emoji are single characters:

    "😀".length  #=> 1
"😀".chars   #=> ["😀"]

    Whereas kaomoji are a combination of multiple characters:

    "^_^".length #=> 3
"^_^".chars  #=> ["^", "_", "^"]

    Matching these is a very different task (and you should ask that in a separate question).