When I run:

```
console.log($('.' + menu_id)[0].className);

```

I get:

```
main-mobile-menu hide-left

```

When I run:

```
console.log($('.' + menu_id)[0].className -= ' hide-left');

```

I get:

```
NaN

```

I can set the class using: 

```
$('.' + menu_id)[0].className = 'main-mobile-menu'

```

but I don't understand why -= is not working. I know there is a removeClass method in jQuery, but I've been trying to use native javascript with jQuery elements when possible.