Unicode trim

gistfile1.js

// Names:    HEAVY BLACK HEART <space> EXTRATERRESTRIAL ALIEN <space> FIRE <space> PILE OF POO
// Unicode:  U+2764                    U+1F47D                        U+1F525      U+1F4A9
// UTF-8     E2 9D A4                  F0 9F 91 BD                    F0 9F 94 A5  F0 9F 92 A9
> var str = '❤ 👽 🔥 💩'

> str
'❤ 👽 🔥 💩'
undefined

> var buf = new Buffer(str, 'utf8')
undefined
> buf
<Buffer e2 9d a4 20 f0 9f 91 bd 20 f0 9f 94 a5 20 f0 9f 92 a9>
> buf.toString('utf8')
'❤ 👽 🔥 💩'
> buf.toString('utf8', 0, 5)
'❤ �'
> var result = buf.toString('utf8', 0, 5)
undefined
> result.charCodeAt(result.length - 1).toString(16)
'fffd'
> result.length
3
> result.charCodeAt(0).toString(16)
'2764'
> result.charCodeAt(1).toString(16)
'20'
> result.charCodeAt(2).toString(16)
'fffd'

> var buf2 = new Buffer(str, 'ucs2')
<Buffer 64 27 20 00 3d d8 7d dc 20 00 3d d8 25 dd 20 00 3d d8 a9 dc>
> var result2 = buf2.toString('utf8', 0, 5)
undefined
> result2
'd\' \u0000='
> result2.length
5
> result2.charCodeAt(0).toString(16)
'64'
> result2.charCodeAt(1).toString(16)
'27'
> result2.charCodeAt(2).toString(16)
'20'
> result2.charCodeAt(3).toString(16)
'0'
> result2.charCodeAt(4).toString(16)
'3d'