We try to avoid same-line comments, but this is one scenario in which I haven't found a satisfactory alternative. I'll throw two options out there, but I don't know if they're any better than the EOL comment.

a. Comment on previous line, using a colon.

```js
// Returns undefined: 
$( "#not-a-progressbar" ).progressbar( "instance" );
```
b. Comment on next line, being a bit more explicit.

```js
var notProgress = $( "#not-a-progressbar" ).progressbar( "instance" );
// notProgress === undefined
```