I found this article had more depth: http://patriciopalladino.com/blog/2012/08/09/non-alphanumeri...
!+[]`$
The parent link above is ES5 and uses 8 characters: !+[](){}
The jsfuck.com ES6 dialect uses 6 characters: !+[]()
jsfuck was previously ES5 but they now rely on ES6isms to shorten their code.