It means it inherits the 'this' of the enclosing function. Without fat arrow: function outer() { function inner() { this === inner.this; } } With fat arrow: f

It means it inherits the 'this' of the enclosing function. Without fat arrow: function outer() { function inner() { this === inner.this; } } With fat arrow: function outer() { var inner = => this === outer.this; }