This was the first result in my google search for: “double vs single quotes typescript.”

Considering the accepted answer is a little old (but still valid from the docs) I would like to add this quote from: https://github.com/Microsoft/TypeScript/wiki/Coding-guidelines updated on November 27, 2015:

Use double quotes for strings.

Granted “the code is more what you’d call ‘guidelines’ than actual rules.” 🙂