About Mozilla Generators

this_and_generators.js

//script type="application/javascript;version=1.7"

function FactorGenMaker(factor) {
  let(j=1){for(;;) yield factor*j++};
}

function NullGenMaker() {
  for(;;) yield null;
}

let (positiveEven = FactorGenMaker(2),
     negativeEven = FactorGenMaker(-2),
     nuller       = NullGenMaker()) {
  console.log('First positiveEven number is 2');
  try {console.log(positiveEven.next.call({})+', if this is an Object');} catch (e) {console.log(e)}
  console.log(positiveEven.next.call(nuller)+', if this is a generator of other class'); 
  console.log(positiveEven.next.call(negativeEven)+', if this is other generator of the same class'); 
  console.log(positiveEven.next.call(positiveEven)+', if this is this');
  
  console.log('[[Class]]:'+/\[object (.*)\]/.exec(Object.prototype.toString.call(positiveEven))[1]);
}

/** 

Output
------

First positiveEven number is 2
TypeError: Generator.prototype.next called on incompatible Object { message="Generator.prototype.nex... on incompatible Object", more...}
null, if this is a generator of other class
-2, if this is other generator of the same class
2, if this is this
[[Class]]:Generator

Therefore
---------

This is the generator object which internal resumable-function will be called.
Exists the Generator Class

*/