[_jnc]

At least in Ruby, you can only do string interpolation with strings in double quotes.

[elisee]

JavaScript up to ES5 doesn't support string interpolation at all. ES6 introduces backticks `before${var}after` for that, but there's still no functional difference between single and double quotes.

[mixmastamyk]

Interesting they chose that, considering it's deprecated in bash and python.

[sprobertson]

Coffeescript as well. I try to use single quotes whenever possible, so if a string is templated it stands out a bit with the double quotes.