Non-string types are handled inconsistently between javascript and html escaping

With the template

```
{name|h|js}{~n}
{name|j|js}{~n}
```

and the context

```
{"name": true}
```

You get the output
```
&quot;true&quot;
true
```

So it seems that html escaping turns non-string types into string, but javascript escaping does not.