Firefox, prior to version 26 implemented another iterator protocol that is similar to the standard ES2015 Iterator protocol.

JavaScript Legacy Iterator

The legacy generator function statement declares legacy generator functions with the specified parameters.

JavaScript Legacy Iterator Reference

The Iterator function returns an object which implements legacy iterator protocol and iterates over enumerable properties of an object.

Deprecated JavaScript Legacy Iterator Reference

The function keyword can be used to define a legacy generator function inside an expression. To make the function a legacy generator, the function body should contain at least one yield expression.

JavaScript Legacy Iterator Reference Référence

The StopIteration object is used to tell the end of the iteration in the legacy iterator protocol.

Deprecated JavaScript Legacy Iterator Reference StopIteration

The Generator object is returned by a generator function and it conforms to both the iterable protocol and the iterator protocol.

ECMAScript6 Generator JavaScript Legacy Generator Legacy Iterator Reference