Iterable and Observable are dual

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interface Iterable {
    Generator @@iterator(Generator);
}

interface Observable {
    Generator observer(Generator);
}

Array.prototype[@@observer] = function(generator) {
    var decoratedGenerator = Object.create(generator),
        done = false;

    ["throw","return"].forEach(method => {
        decoratedGenerator[method] = v => {
            var superMethod = generator[method];
            done = true;
            if (superMethod) {
                return superMethod.call(generator, v);
            }
        }
    });

    for(let x of this) {
        decoratedGenerator.next(x)
        if (done) {
            break;
        }
    }
    if (!done) {
        decoratedGenerator.return();
    }

    return decoratedGenerator;
}

[1,2,3][@@observer]({
    next: function(value) {
        console.log(value);
        if (value ===2 ) {
            this.return();
        }
    }
})

for(let x of [1,2,3]) {
    console.log(value);
    if (x == 2) {
        break;
    }
}

async function test() {
    for(let x on [1,2,3]) {
        console.log(value);
        if (x === 2) {
            break;
        }
    }
}

document.addEventListener("mousemove", function next(e) {

})