Sorry guy's this seems to be an error.
I tried using yield using the Firefox console and it outputted this, but after I actually constructed an actual file and ran it though firefox it behaved as expected
If anyone is curious
<html>
<head>
</head>
<body>
<script type="application/javascript;version=1.7" >
function helloWorld () {
console.log("hello");
yield "world";
yield "END";
}
var sayHello = helloWorld();
console.log(sayHello.next());
function helloWorld1 () {
console.log('hello');
yield console.log("world");
yield "END2";
}
var sayHello1 = helloWorld1();
sayHello1.next();
console.log(sayHello.next());
console.log(sayHello1.next());
</script>
</body>
</html>
outputs:
"hello" "world" "hello" "world" "END" "END2"