import UIKit

let regex = try! NSRegularExpression(pattern: ":[a-zA-Z0-9_]+:", options: [])

func stripCustomEmoji(from string: String) -> String {
    let range = NSRange(location: 0, length: string.utf16.count)
    return regex.stringByReplacingMatches(in: string, options: [], range: range, withTemplate: "")
}

let result = stripCustomEmoji(from: ":sparkles_nb: 🦑 :dizzy_trans:")

stripCustomEmoji(from: ":dizzy_trans:")
stripCustomEmoji(from: " 🦑 :dizzy_trans:")
stripCustomEmoji(from: "  :dizzy_trans:")