Before ES7 swapping 2 values was annoying and counterintuitive, the idea is to store one value in a temporary variable so that you can exchange them, adding extra lines of code. In total you need minimum 3 lines of code to swap to values. Say we want to swap the contents of a and b, we need to introduce a third variable, c:
let a=1, b=2, c; c = a; a = b; b = c;
With ES7, the new way is super simple and intuitive:
let a=1, b=2; [a,b] = [b,a];
Amazing, isn't it? Super simple and just one line!
Hope you enjoyed that one!