How do I remove emoji from string

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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).

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