Swift 5.1 - String javaScriptEscapedString extension

String+javaScriptEscapedString.swift

extension String {
    var javaScriptEscapedString: String {
        // Because JSON is not a subset of JavaScript, the LINE_SEPARATOR and PARAGRAPH_SEPARATOR unicode
        // characters embedded in (valid) JSON will cause the webview's JavaScript parser to error. So we
        // must encode them first. See here: http://timelessrepo.com/json-isnt-a-javascript-subset
        // Also here: http://media.giphy.com/media/wloGlwOXKijy8/giphy.gif
        let str = self.replacingOccurrences(of: "\u{2028}", with: "\\u2028")
                      .replacingOccurrences(of: "\u{2029}", with: "\\u2029")
        // Because escaping JavaScript is a non-trivial task (https://github.com/johnezang/JSONKit/blob/master/JSONKit.m#L1423)
        // we proceed to hax instead:
        do {
            let encoder = JSONEncoder()
            let data = try encoder.encode([str])
            let encodedString = String(decoding: data, as: UTF8.self)
            return String(encodedString.dropLast().dropFirst())
        } catch {
            return self
        }
    }
}