NSJSONSerialization serialization of a string containing forward slashes / and HTML is escaped incorrectly

Question

I am trying to convert some simple HTML into a string value in a JSON object and I\'m having trouble getting the string encoding to not escape the string in NSJSONSerializat

Answer 1

I believeNSJSONSerialization is behaving as designed in regards to encoding HTML.

If you look at some questions (1, 2) on encoding HTML in JSON you'll see the answers always mention escaping the forward slashes.

JSON doesn't require forward slashes to be escaped, but HTML doesn't allow a javascript string to contain </ as it can be confused with the end of the <SCRIPT> tag.

See the answers here, here and most directly the w3.org HTML4 Appendix which states in B.3.2 Specifying non-HTML data

ILLEGAL EXAMPLE: 
The following script data incorrectly contains a "</" sequence (as part of "</EM>") before the SCRIPT end tag:

<SCRIPT type="text/javascript">
  document.write ("<EM>This won't work</EM>")
</SCRIPT>

Although this behaviour may cause issues for you NSJSONSerialisation is just playing by the age old rules of encoding HTML data for use in <SCRIPT> tags.

Answer 2

iOS 13 only: If you're not worried about producing invalid HTML sequences (as described in this answer), you can disable forward-slash escaping by passing the option NSJSONWritingWithoutEscapingSlashes to the serializer.

Example:

jsonData = [NSJSONSerialization dataWithJSONObject:batchUpdates
                                           options:NSJSONWritingWithoutEscapingSlashes
                                             error:nil];

Answer 3

Here's my subclass of AFJSONRequestSerializer to remove \ before / symbols in resulting JSON; handy if you use AFNetworking

class SanitizedAFJSONRequestSerializer: AFJSONRequestSerializer
{
    override func requestBySerializingRequest(request: NSURLRequest!, withParameters parameters: AnyObject!, error: NSErrorPointer) -> NSURLRequest!
    {
        var request = super.requestBySerializingRequest(request, withParameters: parameters, error: error)

        if let jsonData = request.HTTPBody
        {
            if let jsonString = NSString(data: jsonData, encoding: NSUTF8StringEncoding) as? String
            {
                let sanitizedString = jsonString.stringByReplacingOccurrencesOfString("\\/", withString: "/", options: NSStringCompareOptions.CaseInsensitiveSearch, range:nil) as NSString

                println("sanitized json string: \(sanitizedString)")

                var mutableRequest = request.mutableCopy() as! NSMutableURLRequest
                mutableRequest.HTTPBody = sanitizedString.dataUsingEncoding(NSUTF8StringEncoding)
                request = mutableRequest
            }
        }

        return request
    }
}