let b = 10
x: a = b
b // 10
a // 10
x // Uncaught ReferenceError: x is not definedWhat is x and how a exists without declaring it first?
Asked
Active
Viewed 40 times
0
-
3[Labelled statements](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/label) – Pointy May 31 '19 at 09:29
-
2`a` *does* exist, you assigned to it with `a=b` – CertainPerformance May 31 '19 at 09:29
-
2`a` is implicit global. – Maheer Ali May 31 '19 at 09:29
-
1As it stands how OP shows it, it is invalid syntax. – connexo May 31 '19 at 09:30
-
it's not invalid syntax in chrome. maybe in other browsers, it is. – Stav Alfi May 31 '19 at 09:33
-
@connexo no it is not invalid; try it. Any statement can be labelled. – Pointy May 31 '19 at 09:37
-
@Pointy Run it in latest Firefox. `"message": "ReferenceError: x is not defined",` – connexo May 31 '19 at 09:44
-
@connexo sure, that's an error because in fact `x` is not defined as a variable of any kind. The label part, which I think was the point of the question, is fine however. (Pointless, but syntactically correct.) – Pointy May 31 '19 at 09:57