Javascsript generator confusing behavior

I came across this article explaining generators https://modernweb.com/replacing-callbacks-with-es6-generators/

Which contains this example

function* ticketGenerator() {
  for (var i = 0; true; i++) {
    var reset = yield i;
    if (reset) {
      i = -1;
    }
  }
}

var takeANumber = ticketGenerator();
console.log(takeANumber.next().value); //0
console.log(takeANumber.next().value); //1
console.log(takeANumber.next().value); //2
console.log(takeANumber.next(true).value); //0          <----- Why is this happening?
console.log(takeANumber.next().value); //1

What confuses me is the output of the console.log(takeANumber.next(true).value); line which is unintuitive.

Why wouldn't it print 0 1 2 3 0 instead of 0 1 2 0 1 ?

I tried running it in console to make sure there wasn't an error in the article but it worked as the article stated

Solution

You can look at it step by step using Python Visualizer (which can also visualize JavaScript). See here.

What happens is this:

You call next() for the first time. The generator code runs from the beginning to the function until it reaches yield 0. The value 0 is returned and execution is paused.
You call next() for the second time. The generator code receives undefined as return value from the previous yield and continues execution until it reaches yield 1. The value 1 is returned and execution is paused.
You call next() for the third time. The generator code receives undefined as return value from the previous yield and continues execution until it reaches yield 2. The value 2 is returned and execution is paused.
You call next(true). The generator code recevies true as return value from the previous yield and resets the counter to -1. It then continues execution until it reaches yield 0. The value 0 is returned and execution is paused.
You call next() for the last time. The generator code receives undefined as return value from the previous yield and continues execution until it reaches yield 1. The value 1 is returned and execution is paused.