What is `this` inside a new-invoked generator?

# Axel Rauschmayer (10 years ago)

Question: what does the following code snippet log in the last line?

function* gen() {
    yield this;
}
let genObj = new gen();
let [_this] = genObj;
console.log(_this === genObj); // ???

I’m finding three answers:

The spec says [1] that any reference to this in a generator invoked via new causes a ReferenceError.
Firefox logs false for the code snippet.
A year ago, Allen stated [2] that if you invoke a generator function via new, this points to the generator object. On other words, the code snippet would log true.

[1] people.mozilla.org/~jorendorff/es6-draft.html#sec-generator-function-definitions-runtime-semantics-evaluatebody [2] esdiscuss.org/topic/reason-why-generators-do-not-have-references-to-themselves#content

Question: what does the following code snippet log in the last line?

```js
function* gen() {
    yield this;
}
let genObj = new gen();
let [_this] = genObj;
console.log(_this === genObj); // ???
```

I’m finding three answers:

1. The spec says [1] that any reference to `this` in a generator invoked via `new` causes a `ReferenceError`.

2. Firefox logs `false` for the code snippet.

3. A year ago, Allen stated [2] that if you invoke a generator function via `new`, `this` points to the generator object. On other words, the code snippet would log `true`.


[1] https://people.mozilla.org/~jorendorff/es6-draft.html#sec-generator-function-definitions-runtime-semantics-evaluatebody
[2] https://esdiscuss.org/topic/reason-why-generators-do-not-have-references-to-themselves#content-8

-- 
Dr. Axel Rauschmayer
axel at rauschma.de
rauschma.de

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# André Bargull (10 years ago)

Question: what does the following code snippet log in the last line?
function* gen() {
     yield this;
}
let genObj = new gen();
let [_this] = genObj;
console.log(_this === genObj); // ???
I’m finding three answers:

The spec says [1] that any reference to this in a generator invoked via new causes a ReferenceError.

Firefox logs false for the code snippet.

A year ago, Allen stated [2] that if you invoke a generator function via new, this points to the generator object. On other words, the code snippet would log true.

It's a ReferenceError. Future editions may add a meta property to make it possible to retrieve the current generator object (ecmascript#3626).

> Question: what does the following code snippet log in the last line?
>
> ```js
> function* gen() {
>      yield this;
> }
> let genObj = new gen();
> let [_this] = genObj;
> console.log(_this === genObj); // ???
> ```
>
> I’m finding three answers:
>
> 1. The spec says [1] that any reference to `this` in a generator invoked via `new` causes a `ReferenceError`.
>
> 2. Firefox logs `false` for the code snippet.
>
> 3. A year ago, Allen stated [2] that if you invoke a generator function via `new`, `this` points to the generator object. On other words, the code snippet would log `true`.

It's a ReferenceError. Future editions may add a meta property to make it possible to retrieve the 
current generator object (https://bugs.ecmascript.org/show_bug.cgi?id=3626).