I've been wondering about this construct, i.e. separating variable assignments with comas without a heading `var` keyword. It turns out that this is using the [JavaScript's Comma Operator](https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/Comma_Operator?redirectlocale=en-US&redirectslug=JavaScript%2FReference%2FOperators%2FSpecial%2FComma_Operator), which is fine. But it is to be noted that:

```
var i = 1, ii = 10;
```

is not the same as:

```
var i, ii;
i = 1, i = 10;
```

In the second code block, `i = 1, i = 10` is an actual expression that returns the value of the second operand.