[_ar7]

Although it wouldn't work if you were using objects and wanted to do a deep comparison e.g.

    [...new Set([{x: 1}, {x: 1}])]

[AndrewStephens]

Yeah, I recently did a project in Javascript (as a longtime C++ programmer) and was bitten by this exact problem.

Javascript is great but sometimes I miss the predicability of the STL.

[purple-dragon]

... an important observation, for sure.