Keeping escaped unicode caracters

I have an input JSON like this:

{"source":"Subject: NEED: 11/5 BNA-MSL u2013 1200L Departure - 1 Pax"}

I read it with JSON.parse and it reads the u2013 as –, which is fine for display in my app.

However, I need to export again the same JSON, to send it down to some other app. I want to keep the same format and have back the u2013 into the JSON. I am doing JSON.stringify, but it keeps the – in the output.

Any idea what I could do to keep the u syntax?