(![] + [])[+[]] +
(![] + [])[+!+[]] +
([![]] + [][[]])[+!+[] + [+[]]] +
(![] + [])[!+[] + !+[]];
view raw type-coercion.js hosted with ❤ by GitHub

All the credit goes to wtfjs.

PS A deep paper on a matter by Patricio Palladino – Brainfuck beware: JavaScript is after you!