Edit in JSFiddle

//All below return false 
console.log(Boolean(undefined));
console.log(Boolean(null));
console.log(Boolean(0));
console.log(Boolean(''));
console.log(Boolean(NaN));

//All below return true
console.log(Boolean(1));
console.log(Boolean('false'));
console.log(Boolean([]));
console.log(Boolean({}));
console.log(Boolean(function(){}));
console.log(Boolean(/foo/));